From 69c77d6492e1465f30cc1463132e18dadc614dcd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?H=C3=A9ctor=20Ramos?= <hramos@fb.com>
Date: Tue, 20 Mar 2018 17:03:06 -0700
Subject: [PATCH] React sync for revisions ced176e...9d484ed

Reviewed By: bvaughn

Differential Revision: D7338640

fbshipit-source-id: e2d75d2f1795fb3c37f193d15216951c707711d9
---
 Libraries/Renderer/REVISION                   |    2 +-
 Libraries/Renderer/ReactFabric-dev.js         | 2095 ++++++++--------
 Libraries/Renderer/ReactFabric-prod.js        |  671 +++---
 Libraries/Renderer/ReactNativeRenderer-dev.js | 2101 +++++++++--------
 .../Renderer/ReactNativeRenderer-prod.js      |  681 +++---
 Libraries/Renderer/shims/ReactFabric.js       |    5 +
 6 files changed, 2990 insertions(+), 2565 deletions(-)

diff --git a/Libraries/Renderer/REVISION b/Libraries/Renderer/REVISION
index 321055318..7e989de97 100644
--- a/Libraries/Renderer/REVISION
+++ b/Libraries/Renderer/REVISION
@@ -1 +1 @@
-ced176edb7605a25e916895fd060f3943c647fee
\ No newline at end of file
+9d484edc4b64160cb335a23a2cb21667fb2cdf4c
\ No newline at end of file
diff --git a/Libraries/Renderer/ReactFabric-dev.js b/Libraries/Renderer/ReactFabric-dev.js
index e485c5621..22c77f2e0 100644
--- a/Libraries/Renderer/ReactFabric-dev.js
+++ b/Libraries/Renderer/ReactFabric-dev.js
@@ -25,8 +25,8 @@ var deepDiffer = require("deepDiffer");
 var flattenStyle = require("flattenStyle");
 var React = require("react");
 var emptyObject = require("fbjs/lib/emptyObject");
-var checkPropTypes = require("prop-types/checkPropTypes");
 var shallowEqual = require("fbjs/lib/shallowEqual");
+var checkPropTypes = require("prop-types/checkPropTypes");
 var deepFreezeAndThrowOnMutationInDev = require("deepFreezeAndThrowOnMutationInDev");
 var FabricUIManager = require("FabricUIManager");
 
@@ -4134,876 +4134,6 @@ function findCurrentHostFiberWithNoPortals(parent) {
   return null;
 }
 
-var valueStack = [];
-
-var fiberStack = void 0;
-
-{
-  fiberStack = [];
-}
-
-var index = -1;
-
-function createCursor(defaultValue) {
-  return {
-    current: defaultValue
-  };
-}
-
-function pop(cursor, fiber) {
-  if (index < 0) {
-    {
-      warning(false, "Unexpected pop.");
-    }
-    return;
-  }
-
-  {
-    if (fiber !== fiberStack[index]) {
-      warning(false, "Unexpected Fiber popped.");
-    }
-  }
-
-  cursor.current = valueStack[index];
-
-  valueStack[index] = null;
-
-  {
-    fiberStack[index] = null;
-  }
-
-  index--;
-}
-
-function push(cursor, value, fiber) {
-  index++;
-
-  valueStack[index] = cursor.current;
-
-  {
-    fiberStack[index] = fiber;
-  }
-
-  cursor.current = value;
-}
-
-function reset() {
-  while (index > -1) {
-    valueStack[index] = null;
-
-    {
-      fiberStack[index] = null;
-    }
-
-    index--;
-  }
-}
-
-var describeComponentFrame = function(name, source, ownerName) {
-  return (
-    "\n    in " +
-    (name || "Unknown") +
-    (source
-      ? " (at " +
-        source.fileName.replace(/^.*[\\\/]/, "") +
-        ":" +
-        source.lineNumber +
-        ")"
-      : ownerName ? " (created by " + ownerName + ")" : "")
-  );
-};
-
-function describeFiber(fiber) {
-  switch (fiber.tag) {
-    case IndeterminateComponent:
-    case FunctionalComponent:
-    case ClassComponent:
-    case HostComponent:
-      var owner = fiber._debugOwner;
-      var source = fiber._debugSource;
-      var name = getComponentName(fiber);
-      var ownerName = null;
-      if (owner) {
-        ownerName = getComponentName(owner);
-      }
-      return describeComponentFrame(name, source, ownerName);
-    default:
-      return "";
-  }
-}
-
-// This function can only be called with a work-in-progress fiber and
-// only during begin or complete phase. Do not call it under any other
-// circumstances.
-function getStackAddendumByWorkInProgressFiber(workInProgress) {
-  var info = "";
-  var node = workInProgress;
-  do {
-    info += describeFiber(node);
-    // Otherwise this return pointer might point to the wrong tree:
-    node = node["return"];
-  } while (node);
-  return info;
-}
-
-function getCurrentFiberOwnerName() {
-  {
-    var fiber = ReactDebugCurrentFiber.current;
-    if (fiber === null) {
-      return null;
-    }
-    var owner = fiber._debugOwner;
-    if (owner !== null && typeof owner !== "undefined") {
-      return getComponentName(owner);
-    }
-  }
-  return null;
-}
-
-function getCurrentFiberStackAddendum() {
-  {
-    var fiber = ReactDebugCurrentFiber.current;
-    if (fiber === null) {
-      return null;
-    }
-    // Safe because if current fiber exists, we are reconciling,
-    // and it is guaranteed to be the work-in-progress version.
-    return getStackAddendumByWorkInProgressFiber(fiber);
-  }
-  return null;
-}
-
-function resetCurrentFiber() {
-  ReactDebugCurrentFrame.getCurrentStack = null;
-  ReactDebugCurrentFiber.current = null;
-  ReactDebugCurrentFiber.phase = null;
-}
-
-function setCurrentFiber(fiber) {
-  ReactDebugCurrentFrame.getCurrentStack = getCurrentFiberStackAddendum;
-  ReactDebugCurrentFiber.current = fiber;
-  ReactDebugCurrentFiber.phase = null;
-}
-
-function setCurrentPhase(phase) {
-  ReactDebugCurrentFiber.phase = phase;
-}
-
-var ReactDebugCurrentFiber = {
-  current: null,
-  phase: null,
-  resetCurrentFiber: resetCurrentFiber,
-  setCurrentFiber: setCurrentFiber,
-  setCurrentPhase: setCurrentPhase,
-  getCurrentFiberOwnerName: getCurrentFiberOwnerName,
-  getCurrentFiberStackAddendum: getCurrentFiberStackAddendum
-};
-
-var debugRenderPhaseSideEffects = false;
-var debugRenderPhaseSideEffectsForStrictMode = false;
-
-var enableUserTimingAPI = true;
-var enableGetDerivedStateFromCatch = false;
-var warnAboutDeprecatedLifecycles = false;
-var replayFailedUnitOfWorkWithInvokeGuardedCallback = true;
-
-// React Fabric uses persistent reconciler.
-var enableMutatingReconciler = false;
-var enableNoopReconciler = false;
-var enablePersistentReconciler = true;
-
-// Only used in www builds.
-
-// Prefix measurements so that it's possible to filter them.
-// Longer prefixes are hard to read in DevTools.
-var reactEmoji = "\u269B";
-var warningEmoji = "\u26D4";
-var supportsUserTiming =
-  typeof performance !== "undefined" &&
-  typeof performance.mark === "function" &&
-  typeof performance.clearMarks === "function" &&
-  typeof performance.measure === "function" &&
-  typeof performance.clearMeasures === "function";
-
-// Keep track of current fiber so that we know the path to unwind on pause.
-// TODO: this looks the same as nextUnitOfWork in scheduler. Can we unify them?
-var currentFiber = null;
-// If we're in the middle of user code, which fiber and method is it?
-// Reusing `currentFiber` would be confusing for this because user code fiber
-// can change during commit phase too, but we don't need to unwind it (since
-// lifecycles in the commit phase don't resemble a tree).
-var currentPhase = null;
-var currentPhaseFiber = null;
-// Did lifecycle hook schedule an update? This is often a performance problem,
-// so we will keep track of it, and include it in the report.
-// Track commits caused by cascading updates.
-var isCommitting = false;
-var hasScheduledUpdateInCurrentCommit = false;
-var hasScheduledUpdateInCurrentPhase = false;
-var commitCountInCurrentWorkLoop = 0;
-var effectCountInCurrentCommit = 0;
-var isWaitingForCallback = false;
-// During commits, we only show a measurement once per method name
-// to avoid stretch the commit phase with measurement overhead.
-var labelsInCurrentCommit = new Set();
-
-var formatMarkName = function(markName) {
-  return reactEmoji + " " + markName;
-};
-
-var formatLabel = function(label, warning$$1) {
-  var prefix = warning$$1 ? warningEmoji + " " : reactEmoji + " ";
-  var suffix = warning$$1 ? " Warning: " + warning$$1 : "";
-  return "" + prefix + label + suffix;
-};
-
-var beginMark = function(markName) {
-  performance.mark(formatMarkName(markName));
-};
-
-var clearMark = function(markName) {
-  performance.clearMarks(formatMarkName(markName));
-};
-
-var endMark = function(label, markName, warning$$1) {
-  var formattedMarkName = formatMarkName(markName);
-  var formattedLabel = formatLabel(label, warning$$1);
-  try {
-    performance.measure(formattedLabel, formattedMarkName);
-  } catch (err) {}
-  // If previous mark was missing for some reason, this will throw.
-  // This could only happen if React crashed in an unexpected place earlier.
-  // Don't pile on with more errors.
-
-  // Clear marks immediately to avoid growing buffer.
-  performance.clearMarks(formattedMarkName);
-  performance.clearMeasures(formattedLabel);
-};
-
-var getFiberMarkName = function(label, debugID) {
-  return label + " (#" + debugID + ")";
-};
-
-var getFiberLabel = function(componentName, isMounted, phase) {
-  if (phase === null) {
-    // These are composite component total time measurements.
-    return componentName + " [" + (isMounted ? "update" : "mount") + "]";
-  } else {
-    // Composite component methods.
-    return componentName + "." + phase;
-  }
-};
-
-var beginFiberMark = function(fiber, phase) {
-  var componentName = getComponentName(fiber) || "Unknown";
-  var debugID = fiber._debugID;
-  var isMounted = fiber.alternate !== null;
-  var label = getFiberLabel(componentName, isMounted, phase);
-
-  if (isCommitting && labelsInCurrentCommit.has(label)) {
-    // During the commit phase, we don't show duplicate labels because
-    // there is a fixed overhead for every measurement, and we don't
-    // want to stretch the commit phase beyond necessary.
-    return false;
-  }
-  labelsInCurrentCommit.add(label);
-
-  var markName = getFiberMarkName(label, debugID);
-  beginMark(markName);
-  return true;
-};
-
-var clearFiberMark = function(fiber, phase) {
-  var componentName = getComponentName(fiber) || "Unknown";
-  var debugID = fiber._debugID;
-  var isMounted = fiber.alternate !== null;
-  var label = getFiberLabel(componentName, isMounted, phase);
-  var markName = getFiberMarkName(label, debugID);
-  clearMark(markName);
-};
-
-var endFiberMark = function(fiber, phase, warning$$1) {
-  var componentName = getComponentName(fiber) || "Unknown";
-  var debugID = fiber._debugID;
-  var isMounted = fiber.alternate !== null;
-  var label = getFiberLabel(componentName, isMounted, phase);
-  var markName = getFiberMarkName(label, debugID);
-  endMark(label, markName, warning$$1);
-};
-
-var shouldIgnoreFiber = function(fiber) {
-  // Host components should be skipped in the timeline.
-  // We could check typeof fiber.type, but does this work with RN?
-  switch (fiber.tag) {
-    case HostRoot:
-    case HostComponent:
-    case HostText:
-    case HostPortal:
-    case CallComponent:
-    case ReturnComponent:
-    case Fragment:
-    case ContextProvider:
-    case ContextConsumer:
-      return true;
-    default:
-      return false;
-  }
-};
-
-var clearPendingPhaseMeasurement = function() {
-  if (currentPhase !== null && currentPhaseFiber !== null) {
-    clearFiberMark(currentPhaseFiber, currentPhase);
-  }
-  currentPhaseFiber = null;
-  currentPhase = null;
-  hasScheduledUpdateInCurrentPhase = false;
-};
-
-var pauseTimers = function() {
-  // Stops all currently active measurements so that they can be resumed
-  // if we continue in a later deferred loop from the same unit of work.
-  var fiber = currentFiber;
-  while (fiber) {
-    if (fiber._debugIsCurrentlyTiming) {
-      endFiberMark(fiber, null, null);
-    }
-    fiber = fiber["return"];
-  }
-};
-
-var resumeTimersRecursively = function(fiber) {
-  if (fiber["return"] !== null) {
-    resumeTimersRecursively(fiber["return"]);
-  }
-  if (fiber._debugIsCurrentlyTiming) {
-    beginFiberMark(fiber, null);
-  }
-};
-
-var resumeTimers = function() {
-  // Resumes all measurements that were active during the last deferred loop.
-  if (currentFiber !== null) {
-    resumeTimersRecursively(currentFiber);
-  }
-};
-
-function recordEffect() {
-  if (enableUserTimingAPI) {
-    effectCountInCurrentCommit++;
-  }
-}
-
-function recordScheduleUpdate() {
-  if (enableUserTimingAPI) {
-    if (isCommitting) {
-      hasScheduledUpdateInCurrentCommit = true;
-    }
-    if (
-      currentPhase !== null &&
-      currentPhase !== "componentWillMount" &&
-      currentPhase !== "componentWillReceiveProps"
-    ) {
-      hasScheduledUpdateInCurrentPhase = true;
-    }
-  }
-}
-
-function startRequestCallbackTimer() {
-  if (enableUserTimingAPI) {
-    if (supportsUserTiming && !isWaitingForCallback) {
-      isWaitingForCallback = true;
-      beginMark("(Waiting for async callback...)");
-    }
-  }
-}
-
-function stopRequestCallbackTimer(didExpire) {
-  if (enableUserTimingAPI) {
-    if (supportsUserTiming) {
-      isWaitingForCallback = false;
-      var warning$$1 = didExpire ? "React was blocked by main thread" : null;
-      endMark(
-        "(Waiting for async callback...)",
-        "(Waiting for async callback...)",
-        warning$$1
-      );
-    }
-  }
-}
-
-function startWorkTimer(fiber) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
-      return;
-    }
-    // If we pause, this is the fiber to unwind from.
-    currentFiber = fiber;
-    if (!beginFiberMark(fiber, null)) {
-      return;
-    }
-    fiber._debugIsCurrentlyTiming = true;
-  }
-}
-
-function cancelWorkTimer(fiber) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
-      return;
-    }
-    // Remember we shouldn't complete measurement for this fiber.
-    // Otherwise flamechart will be deep even for small updates.
-    fiber._debugIsCurrentlyTiming = false;
-    clearFiberMark(fiber, null);
-  }
-}
-
-function stopWorkTimer(fiber) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
-      return;
-    }
-    // If we pause, its parent is the fiber to unwind from.
-    currentFiber = fiber["return"];
-    if (!fiber._debugIsCurrentlyTiming) {
-      return;
-    }
-    fiber._debugIsCurrentlyTiming = false;
-    endFiberMark(fiber, null, null);
-  }
-}
-
-function stopFailedWorkTimer(fiber) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
-      return;
-    }
-    // If we pause, its parent is the fiber to unwind from.
-    currentFiber = fiber["return"];
-    if (!fiber._debugIsCurrentlyTiming) {
-      return;
-    }
-    fiber._debugIsCurrentlyTiming = false;
-    var warning$$1 = "An error was thrown inside this error boundary";
-    endFiberMark(fiber, null, warning$$1);
-  }
-}
-
-function startPhaseTimer(fiber, phase) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    clearPendingPhaseMeasurement();
-    if (!beginFiberMark(fiber, phase)) {
-      return;
-    }
-    currentPhaseFiber = fiber;
-    currentPhase = phase;
-  }
-}
-
-function stopPhaseTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    if (currentPhase !== null && currentPhaseFiber !== null) {
-      var warning$$1 = hasScheduledUpdateInCurrentPhase
-        ? "Scheduled a cascading update"
-        : null;
-      endFiberMark(currentPhaseFiber, currentPhase, warning$$1);
-    }
-    currentPhase = null;
-    currentPhaseFiber = null;
-  }
-}
-
-function startWorkLoopTimer(nextUnitOfWork) {
-  if (enableUserTimingAPI) {
-    currentFiber = nextUnitOfWork;
-    if (!supportsUserTiming) {
-      return;
-    }
-    commitCountInCurrentWorkLoop = 0;
-    // This is top level call.
-    // Any other measurements are performed within.
-    beginMark("(React Tree Reconciliation)");
-    // Resume any measurements that were in progress during the last loop.
-    resumeTimers();
-  }
-}
-
-function stopWorkLoopTimer(interruptedBy) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    var warning$$1 = null;
-    if (interruptedBy !== null) {
-      if (interruptedBy.tag === HostRoot) {
-        warning$$1 = "A top-level update interrupted the previous render";
-      } else {
-        var componentName = getComponentName(interruptedBy) || "Unknown";
-        warning$$1 =
-          "An update to " + componentName + " interrupted the previous render";
-      }
-    } else if (commitCountInCurrentWorkLoop > 1) {
-      warning$$1 = "There were cascading updates";
-    }
-    commitCountInCurrentWorkLoop = 0;
-    // Pause any measurements until the next loop.
-    pauseTimers();
-    endMark(
-      "(React Tree Reconciliation)",
-      "(React Tree Reconciliation)",
-      warning$$1
-    );
-  }
-}
-
-function startCommitTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    isCommitting = true;
-    hasScheduledUpdateInCurrentCommit = false;
-    labelsInCurrentCommit.clear();
-    beginMark("(Committing Changes)");
-  }
-}
-
-function stopCommitTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-
-    var warning$$1 = null;
-    if (hasScheduledUpdateInCurrentCommit) {
-      warning$$1 = "Lifecycle hook scheduled a cascading update";
-    } else if (commitCountInCurrentWorkLoop > 0) {
-      warning$$1 = "Caused by a cascading update in earlier commit";
-    }
-    hasScheduledUpdateInCurrentCommit = false;
-    commitCountInCurrentWorkLoop++;
-    isCommitting = false;
-    labelsInCurrentCommit.clear();
-
-    endMark("(Committing Changes)", "(Committing Changes)", warning$$1);
-  }
-}
-
-function startCommitHostEffectsTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    effectCountInCurrentCommit = 0;
-    beginMark("(Committing Host Effects)");
-  }
-}
-
-function stopCommitHostEffectsTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    var count = effectCountInCurrentCommit;
-    effectCountInCurrentCommit = 0;
-    endMark(
-      "(Committing Host Effects: " + count + " Total)",
-      "(Committing Host Effects)",
-      null
-    );
-  }
-}
-
-function startCommitLifeCyclesTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    effectCountInCurrentCommit = 0;
-    beginMark("(Calling Lifecycle Methods)");
-  }
-}
-
-function stopCommitLifeCyclesTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    var count = effectCountInCurrentCommit;
-    effectCountInCurrentCommit = 0;
-    endMark(
-      "(Calling Lifecycle Methods: " + count + " Total)",
-      "(Calling Lifecycle Methods)",
-      null
-    );
-  }
-}
-
-var warnedAboutMissingGetChildContext = void 0;
-
-{
-  warnedAboutMissingGetChildContext = {};
-}
-
-// A cursor to the current merged context object on the stack.
-var contextStackCursor = createCursor(emptyObject);
-// A cursor to a boolean indicating whether the context has changed.
-var didPerformWorkStackCursor = createCursor(false);
-// Keep track of the previous context object that was on the stack.
-// We use this to get access to the parent context after we have already
-// pushed the next context provider, and now need to merge their contexts.
-var previousContext = emptyObject;
-
-function getUnmaskedContext(workInProgress) {
-  var hasOwnContext = isContextProvider(workInProgress);
-  if (hasOwnContext) {
-    // If the fiber is a context provider itself, when we read its context
-    // we have already pushed its own child context on the stack. A context
-    // provider should not "see" its own child context. Therefore we read the
-    // previous (parent) context instead for a context provider.
-    return previousContext;
-  }
-  return contextStackCursor.current;
-}
-
-function cacheContext(workInProgress, unmaskedContext, maskedContext) {
-  var instance = workInProgress.stateNode;
-  instance.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext;
-  instance.__reactInternalMemoizedMaskedChildContext = maskedContext;
-}
-
-function getMaskedContext(workInProgress, unmaskedContext) {
-  var type = workInProgress.type;
-  var contextTypes = type.contextTypes;
-  if (!contextTypes) {
-    return emptyObject;
-  }
-
-  // Avoid recreating masked context unless unmasked context has changed.
-  // Failing to do this will result in unnecessary calls to componentWillReceiveProps.
-  // This may trigger infinite loops if componentWillReceiveProps calls setState.
-  var instance = workInProgress.stateNode;
-  if (
-    instance &&
-    instance.__reactInternalMemoizedUnmaskedChildContext === unmaskedContext
-  ) {
-    return instance.__reactInternalMemoizedMaskedChildContext;
-  }
-
-  var context = {};
-  for (var key in contextTypes) {
-    context[key] = unmaskedContext[key];
-  }
-
-  {
-    var name = getComponentName(workInProgress) || "Unknown";
-    checkPropTypes(
-      contextTypes,
-      context,
-      "context",
-      name,
-      ReactDebugCurrentFiber.getCurrentFiberStackAddendum
-    );
-  }
-
-  // Cache unmasked context so we can avoid recreating masked context unless necessary.
-  // Context is created before the class component is instantiated so check for instance.
-  if (instance) {
-    cacheContext(workInProgress, unmaskedContext, context);
-  }
-
-  return context;
-}
-
-function hasContextChanged() {
-  return didPerformWorkStackCursor.current;
-}
-
-function isContextConsumer(fiber) {
-  return fiber.tag === ClassComponent && fiber.type.contextTypes != null;
-}
-
-function isContextProvider(fiber) {
-  return fiber.tag === ClassComponent && fiber.type.childContextTypes != null;
-}
-
-function popContextProvider(fiber) {
-  if (!isContextProvider(fiber)) {
-    return;
-  }
-
-  pop(didPerformWorkStackCursor, fiber);
-  pop(contextStackCursor, fiber);
-}
-
-function popTopLevelContextObject(fiber) {
-  pop(didPerformWorkStackCursor, fiber);
-  pop(contextStackCursor, fiber);
-}
-
-function pushTopLevelContextObject(fiber, context, didChange) {
-  invariant(
-    contextStackCursor.cursor == null,
-    "Unexpected context found on stack. " +
-      "This error is likely caused by a bug in React. Please file an issue."
-  );
-
-  push(contextStackCursor, context, fiber);
-  push(didPerformWorkStackCursor, didChange, fiber);
-}
-
-function processChildContext(fiber, parentContext) {
-  var instance = fiber.stateNode;
-  var childContextTypes = fiber.type.childContextTypes;
-
-  // TODO (bvaughn) Replace this behavior with an invariant() in the future.
-  // It has only been added in Fiber to match the (unintentional) behavior in Stack.
-  if (typeof instance.getChildContext !== "function") {
-    {
-      var componentName = getComponentName(fiber) || "Unknown";
-
-      if (!warnedAboutMissingGetChildContext[componentName]) {
-        warnedAboutMissingGetChildContext[componentName] = true;
-        warning(
-          false,
-          "%s.childContextTypes is specified but there is no getChildContext() method " +
-            "on the instance. You can either define getChildContext() on %s or remove " +
-            "childContextTypes from it.",
-          componentName,
-          componentName
-        );
-      }
-    }
-    return parentContext;
-  }
-
-  var childContext = void 0;
-  {
-    ReactDebugCurrentFiber.setCurrentPhase("getChildContext");
-  }
-  startPhaseTimer(fiber, "getChildContext");
-  childContext = instance.getChildContext();
-  stopPhaseTimer();
-  {
-    ReactDebugCurrentFiber.setCurrentPhase(null);
-  }
-  for (var contextKey in childContext) {
-    invariant(
-      contextKey in childContextTypes,
-      '%s.getChildContext(): key "%s" is not defined in childContextTypes.',
-      getComponentName(fiber) || "Unknown",
-      contextKey
-    );
-  }
-  {
-    var name = getComponentName(fiber) || "Unknown";
-    checkPropTypes(
-      childContextTypes,
-      childContext,
-      "child context",
-      name,
-      // In practice, there is one case in which we won't get a stack. It's when
-      // somebody calls unstable_renderSubtreeIntoContainer() and we process
-      // context from the parent component instance. The stack will be missing
-      // because it's outside of the reconciliation, and so the pointer has not
-      // been set. This is rare and doesn't matter. We'll also remove that API.
-      ReactDebugCurrentFiber.getCurrentFiberStackAddendum
-    );
-  }
-
-  return Object.assign({}, parentContext, childContext);
-}
-
-function pushContextProvider(workInProgress) {
-  if (!isContextProvider(workInProgress)) {
-    return false;
-  }
-
-  var instance = workInProgress.stateNode;
-  // We push the context as early as possible to ensure stack integrity.
-  // If the instance does not exist yet, we will push null at first,
-  // and replace it on the stack later when invalidating the context.
-  var memoizedMergedChildContext =
-    (instance && instance.__reactInternalMemoizedMergedChildContext) ||
-    emptyObject;
-
-  // Remember the parent context so we can merge with it later.
-  // Inherit the parent's did-perform-work value to avoid inadvertently blocking updates.
-  previousContext = contextStackCursor.current;
-  push(contextStackCursor, memoizedMergedChildContext, workInProgress);
-  push(
-    didPerformWorkStackCursor,
-    didPerformWorkStackCursor.current,
-    workInProgress
-  );
-
-  return true;
-}
-
-function invalidateContextProvider(workInProgress, didChange) {
-  var instance = workInProgress.stateNode;
-  invariant(
-    instance,
-    "Expected to have an instance by this point. " +
-      "This error is likely caused by a bug in React. Please file an issue."
-  );
-
-  if (didChange) {
-    // Merge parent and own context.
-    // Skip this if we're not updating due to sCU.
-    // This avoids unnecessarily recomputing memoized values.
-    var mergedContext = processChildContext(workInProgress, previousContext);
-    instance.__reactInternalMemoizedMergedChildContext = mergedContext;
-
-    // Replace the old (or empty) context with the new one.
-    // It is important to unwind the context in the reverse order.
-    pop(didPerformWorkStackCursor, workInProgress);
-    pop(contextStackCursor, workInProgress);
-    // Now push the new context and mark that it has changed.
-    push(contextStackCursor, mergedContext, workInProgress);
-    push(didPerformWorkStackCursor, didChange, workInProgress);
-  } else {
-    pop(didPerformWorkStackCursor, workInProgress);
-    push(didPerformWorkStackCursor, didChange, workInProgress);
-  }
-}
-
-function resetContext() {
-  previousContext = emptyObject;
-  contextStackCursor.current = emptyObject;
-  didPerformWorkStackCursor.current = false;
-}
-
-function findCurrentUnmaskedContext(fiber) {
-  // Currently this is only used with renderSubtreeIntoContainer; not sure if it
-  // makes sense elsewhere
-  invariant(
-    isFiberMounted(fiber) && fiber.tag === ClassComponent,
-    "Expected subtree parent to be a mounted class component. " +
-      "This error is likely caused by a bug in React. Please file an issue."
-  );
-
-  var node = fiber;
-  while (node.tag !== HostRoot) {
-    if (isContextProvider(node)) {
-      return node.stateNode.__reactInternalMemoizedMergedChildContext;
-    }
-    var parent = node["return"];
-    invariant(
-      parent,
-      "Found unexpected detached subtree parent. " +
-        "This error is likely caused by a bug in React. Please file an issue."
-    );
-    node = parent;
-  }
-  return node.stateNode.context;
-}
-
 // Max 31 bit integer. The max integer size in V8 for 32-bit systems.
 // Math.pow(2, 30) - 1
 // 0b111111111111111111111111111111
@@ -5441,6 +4571,53 @@ function onCommitUnmount(fiber) {
   }
 }
 
+var describeComponentFrame = function(name, source, ownerName) {
+  return (
+    "\n    in " +
+    (name || "Unknown") +
+    (source
+      ? " (at " +
+        source.fileName.replace(/^.*[\\\/]/, "") +
+        ":" +
+        source.lineNumber +
+        ")"
+      : ownerName ? " (created by " + ownerName + ")" : "")
+  );
+};
+
+function describeFiber(fiber) {
+  switch (fiber.tag) {
+    case IndeterminateComponent:
+    case FunctionalComponent:
+    case ClassComponent:
+    case HostComponent:
+      var owner = fiber._debugOwner;
+      var source = fiber._debugSource;
+      var name = getComponentName(fiber);
+      var ownerName = null;
+      if (owner) {
+        ownerName = getComponentName(owner);
+      }
+      return describeComponentFrame(name, source, ownerName);
+    default:
+      return "";
+  }
+}
+
+// This function can only be called with a work-in-progress fiber and
+// only during begin or complete phase. Do not call it under any other
+// circumstances.
+function getStackAddendumByWorkInProgressFiber(workInProgress) {
+  var info = "";
+  var node = workInProgress;
+  do {
+    info += describeFiber(node);
+    // Otherwise this return pointer might point to the wrong tree:
+    node = node["return"];
+  } while (node);
+  return info;
+}
+
 /**
  * Forked from fbjs/warning:
  * https://github.com/facebook/fbjs/blob/e66ba20ad5be433eb54423f2b097d829324d9de6/packages/fbjs/src/__forks__/warning.js
@@ -5775,6 +4952,504 @@ var ReactStrictModeWarnings = {
   };
 }
 
+var debugRenderPhaseSideEffects = false;
+var debugRenderPhaseSideEffectsForStrictMode = false;
+
+var enableUserTimingAPI = true;
+var enableGetDerivedStateFromCatch = false;
+var warnAboutDeprecatedLifecycles = false;
+var replayFailedUnitOfWorkWithInvokeGuardedCallback = true;
+
+// React Fabric uses persistent reconciler.
+var enableMutatingReconciler = false;
+var enableNoopReconciler = false;
+var enablePersistentReconciler = true;
+
+// Only used in www builds.
+
+function getCurrentFiberOwnerName() {
+  {
+    var fiber = ReactDebugCurrentFiber.current;
+    if (fiber === null) {
+      return null;
+    }
+    var owner = fiber._debugOwner;
+    if (owner !== null && typeof owner !== "undefined") {
+      return getComponentName(owner);
+    }
+  }
+  return null;
+}
+
+function getCurrentFiberStackAddendum() {
+  {
+    var fiber = ReactDebugCurrentFiber.current;
+    if (fiber === null) {
+      return null;
+    }
+    // Safe because if current fiber exists, we are reconciling,
+    // and it is guaranteed to be the work-in-progress version.
+    return getStackAddendumByWorkInProgressFiber(fiber);
+  }
+  return null;
+}
+
+function resetCurrentFiber() {
+  ReactDebugCurrentFrame.getCurrentStack = null;
+  ReactDebugCurrentFiber.current = null;
+  ReactDebugCurrentFiber.phase = null;
+}
+
+function setCurrentFiber(fiber) {
+  ReactDebugCurrentFrame.getCurrentStack = getCurrentFiberStackAddendum;
+  ReactDebugCurrentFiber.current = fiber;
+  ReactDebugCurrentFiber.phase = null;
+}
+
+function setCurrentPhase(phase) {
+  ReactDebugCurrentFiber.phase = phase;
+}
+
+var ReactDebugCurrentFiber = {
+  current: null,
+  phase: null,
+  resetCurrentFiber: resetCurrentFiber,
+  setCurrentFiber: setCurrentFiber,
+  setCurrentPhase: setCurrentPhase,
+  getCurrentFiberOwnerName: getCurrentFiberOwnerName,
+  getCurrentFiberStackAddendum: getCurrentFiberStackAddendum
+};
+
+// Prefix measurements so that it's possible to filter them.
+// Longer prefixes are hard to read in DevTools.
+var reactEmoji = "\u269B";
+var warningEmoji = "\u26D4";
+var supportsUserTiming =
+  typeof performance !== "undefined" &&
+  typeof performance.mark === "function" &&
+  typeof performance.clearMarks === "function" &&
+  typeof performance.measure === "function" &&
+  typeof performance.clearMeasures === "function";
+
+// Keep track of current fiber so that we know the path to unwind on pause.
+// TODO: this looks the same as nextUnitOfWork in scheduler. Can we unify them?
+var currentFiber = null;
+// If we're in the middle of user code, which fiber and method is it?
+// Reusing `currentFiber` would be confusing for this because user code fiber
+// can change during commit phase too, but we don't need to unwind it (since
+// lifecycles in the commit phase don't resemble a tree).
+var currentPhase = null;
+var currentPhaseFiber = null;
+// Did lifecycle hook schedule an update? This is often a performance problem,
+// so we will keep track of it, and include it in the report.
+// Track commits caused by cascading updates.
+var isCommitting = false;
+var hasScheduledUpdateInCurrentCommit = false;
+var hasScheduledUpdateInCurrentPhase = false;
+var commitCountInCurrentWorkLoop = 0;
+var effectCountInCurrentCommit = 0;
+var isWaitingForCallback = false;
+// During commits, we only show a measurement once per method name
+// to avoid stretch the commit phase with measurement overhead.
+var labelsInCurrentCommit = new Set();
+
+var formatMarkName = function(markName) {
+  return reactEmoji + " " + markName;
+};
+
+var formatLabel = function(label, warning$$1) {
+  var prefix = warning$$1 ? warningEmoji + " " : reactEmoji + " ";
+  var suffix = warning$$1 ? " Warning: " + warning$$1 : "";
+  return "" + prefix + label + suffix;
+};
+
+var beginMark = function(markName) {
+  performance.mark(formatMarkName(markName));
+};
+
+var clearMark = function(markName) {
+  performance.clearMarks(formatMarkName(markName));
+};
+
+var endMark = function(label, markName, warning$$1) {
+  var formattedMarkName = formatMarkName(markName);
+  var formattedLabel = formatLabel(label, warning$$1);
+  try {
+    performance.measure(formattedLabel, formattedMarkName);
+  } catch (err) {}
+  // If previous mark was missing for some reason, this will throw.
+  // This could only happen if React crashed in an unexpected place earlier.
+  // Don't pile on with more errors.
+
+  // Clear marks immediately to avoid growing buffer.
+  performance.clearMarks(formattedMarkName);
+  performance.clearMeasures(formattedLabel);
+};
+
+var getFiberMarkName = function(label, debugID) {
+  return label + " (#" + debugID + ")";
+};
+
+var getFiberLabel = function(componentName, isMounted, phase) {
+  if (phase === null) {
+    // These are composite component total time measurements.
+    return componentName + " [" + (isMounted ? "update" : "mount") + "]";
+  } else {
+    // Composite component methods.
+    return componentName + "." + phase;
+  }
+};
+
+var beginFiberMark = function(fiber, phase) {
+  var componentName = getComponentName(fiber) || "Unknown";
+  var debugID = fiber._debugID;
+  var isMounted = fiber.alternate !== null;
+  var label = getFiberLabel(componentName, isMounted, phase);
+
+  if (isCommitting && labelsInCurrentCommit.has(label)) {
+    // During the commit phase, we don't show duplicate labels because
+    // there is a fixed overhead for every measurement, and we don't
+    // want to stretch the commit phase beyond necessary.
+    return false;
+  }
+  labelsInCurrentCommit.add(label);
+
+  var markName = getFiberMarkName(label, debugID);
+  beginMark(markName);
+  return true;
+};
+
+var clearFiberMark = function(fiber, phase) {
+  var componentName = getComponentName(fiber) || "Unknown";
+  var debugID = fiber._debugID;
+  var isMounted = fiber.alternate !== null;
+  var label = getFiberLabel(componentName, isMounted, phase);
+  var markName = getFiberMarkName(label, debugID);
+  clearMark(markName);
+};
+
+var endFiberMark = function(fiber, phase, warning$$1) {
+  var componentName = getComponentName(fiber) || "Unknown";
+  var debugID = fiber._debugID;
+  var isMounted = fiber.alternate !== null;
+  var label = getFiberLabel(componentName, isMounted, phase);
+  var markName = getFiberMarkName(label, debugID);
+  endMark(label, markName, warning$$1);
+};
+
+var shouldIgnoreFiber = function(fiber) {
+  // Host components should be skipped in the timeline.
+  // We could check typeof fiber.type, but does this work with RN?
+  switch (fiber.tag) {
+    case HostRoot:
+    case HostComponent:
+    case HostText:
+    case HostPortal:
+    case CallComponent:
+    case ReturnComponent:
+    case Fragment:
+    case ContextProvider:
+    case ContextConsumer:
+      return true;
+    default:
+      return false;
+  }
+};
+
+var clearPendingPhaseMeasurement = function() {
+  if (currentPhase !== null && currentPhaseFiber !== null) {
+    clearFiberMark(currentPhaseFiber, currentPhase);
+  }
+  currentPhaseFiber = null;
+  currentPhase = null;
+  hasScheduledUpdateInCurrentPhase = false;
+};
+
+var pauseTimers = function() {
+  // Stops all currently active measurements so that they can be resumed
+  // if we continue in a later deferred loop from the same unit of work.
+  var fiber = currentFiber;
+  while (fiber) {
+    if (fiber._debugIsCurrentlyTiming) {
+      endFiberMark(fiber, null, null);
+    }
+    fiber = fiber["return"];
+  }
+};
+
+var resumeTimersRecursively = function(fiber) {
+  if (fiber["return"] !== null) {
+    resumeTimersRecursively(fiber["return"]);
+  }
+  if (fiber._debugIsCurrentlyTiming) {
+    beginFiberMark(fiber, null);
+  }
+};
+
+var resumeTimers = function() {
+  // Resumes all measurements that were active during the last deferred loop.
+  if (currentFiber !== null) {
+    resumeTimersRecursively(currentFiber);
+  }
+};
+
+function recordEffect() {
+  if (enableUserTimingAPI) {
+    effectCountInCurrentCommit++;
+  }
+}
+
+function recordScheduleUpdate() {
+  if (enableUserTimingAPI) {
+    if (isCommitting) {
+      hasScheduledUpdateInCurrentCommit = true;
+    }
+    if (
+      currentPhase !== null &&
+      currentPhase !== "componentWillMount" &&
+      currentPhase !== "componentWillReceiveProps"
+    ) {
+      hasScheduledUpdateInCurrentPhase = true;
+    }
+  }
+}
+
+function startRequestCallbackTimer() {
+  if (enableUserTimingAPI) {
+    if (supportsUserTiming && !isWaitingForCallback) {
+      isWaitingForCallback = true;
+      beginMark("(Waiting for async callback...)");
+    }
+  }
+}
+
+function stopRequestCallbackTimer(didExpire) {
+  if (enableUserTimingAPI) {
+    if (supportsUserTiming) {
+      isWaitingForCallback = false;
+      var warning$$1 = didExpire ? "React was blocked by main thread" : null;
+      endMark(
+        "(Waiting for async callback...)",
+        "(Waiting for async callback...)",
+        warning$$1
+      );
+    }
+  }
+}
+
+function startWorkTimer(fiber) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
+      return;
+    }
+    // If we pause, this is the fiber to unwind from.
+    currentFiber = fiber;
+    if (!beginFiberMark(fiber, null)) {
+      return;
+    }
+    fiber._debugIsCurrentlyTiming = true;
+  }
+}
+
+function cancelWorkTimer(fiber) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
+      return;
+    }
+    // Remember we shouldn't complete measurement for this fiber.
+    // Otherwise flamechart will be deep even for small updates.
+    fiber._debugIsCurrentlyTiming = false;
+    clearFiberMark(fiber, null);
+  }
+}
+
+function stopWorkTimer(fiber) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
+      return;
+    }
+    // If we pause, its parent is the fiber to unwind from.
+    currentFiber = fiber["return"];
+    if (!fiber._debugIsCurrentlyTiming) {
+      return;
+    }
+    fiber._debugIsCurrentlyTiming = false;
+    endFiberMark(fiber, null, null);
+  }
+}
+
+function stopFailedWorkTimer(fiber) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
+      return;
+    }
+    // If we pause, its parent is the fiber to unwind from.
+    currentFiber = fiber["return"];
+    if (!fiber._debugIsCurrentlyTiming) {
+      return;
+    }
+    fiber._debugIsCurrentlyTiming = false;
+    var warning$$1 = "An error was thrown inside this error boundary";
+    endFiberMark(fiber, null, warning$$1);
+  }
+}
+
+function startPhaseTimer(fiber, phase) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    clearPendingPhaseMeasurement();
+    if (!beginFiberMark(fiber, phase)) {
+      return;
+    }
+    currentPhaseFiber = fiber;
+    currentPhase = phase;
+  }
+}
+
+function stopPhaseTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    if (currentPhase !== null && currentPhaseFiber !== null) {
+      var warning$$1 = hasScheduledUpdateInCurrentPhase
+        ? "Scheduled a cascading update"
+        : null;
+      endFiberMark(currentPhaseFiber, currentPhase, warning$$1);
+    }
+    currentPhase = null;
+    currentPhaseFiber = null;
+  }
+}
+
+function startWorkLoopTimer(nextUnitOfWork) {
+  if (enableUserTimingAPI) {
+    currentFiber = nextUnitOfWork;
+    if (!supportsUserTiming) {
+      return;
+    }
+    commitCountInCurrentWorkLoop = 0;
+    // This is top level call.
+    // Any other measurements are performed within.
+    beginMark("(React Tree Reconciliation)");
+    // Resume any measurements that were in progress during the last loop.
+    resumeTimers();
+  }
+}
+
+function stopWorkLoopTimer(interruptedBy) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    var warning$$1 = null;
+    if (interruptedBy !== null) {
+      if (interruptedBy.tag === HostRoot) {
+        warning$$1 = "A top-level update interrupted the previous render";
+      } else {
+        var componentName = getComponentName(interruptedBy) || "Unknown";
+        warning$$1 =
+          "An update to " + componentName + " interrupted the previous render";
+      }
+    } else if (commitCountInCurrentWorkLoop > 1) {
+      warning$$1 = "There were cascading updates";
+    }
+    commitCountInCurrentWorkLoop = 0;
+    // Pause any measurements until the next loop.
+    pauseTimers();
+    endMark(
+      "(React Tree Reconciliation)",
+      "(React Tree Reconciliation)",
+      warning$$1
+    );
+  }
+}
+
+function startCommitTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    isCommitting = true;
+    hasScheduledUpdateInCurrentCommit = false;
+    labelsInCurrentCommit.clear();
+    beginMark("(Committing Changes)");
+  }
+}
+
+function stopCommitTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+
+    var warning$$1 = null;
+    if (hasScheduledUpdateInCurrentCommit) {
+      warning$$1 = "Lifecycle hook scheduled a cascading update";
+    } else if (commitCountInCurrentWorkLoop > 0) {
+      warning$$1 = "Caused by a cascading update in earlier commit";
+    }
+    hasScheduledUpdateInCurrentCommit = false;
+    commitCountInCurrentWorkLoop++;
+    isCommitting = false;
+    labelsInCurrentCommit.clear();
+
+    endMark("(Committing Changes)", "(Committing Changes)", warning$$1);
+  }
+}
+
+function startCommitHostEffectsTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    effectCountInCurrentCommit = 0;
+    beginMark("(Committing Host Effects)");
+  }
+}
+
+function stopCommitHostEffectsTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    var count = effectCountInCurrentCommit;
+    effectCountInCurrentCommit = 0;
+    endMark(
+      "(Committing Host Effects: " + count + " Total)",
+      "(Committing Host Effects)",
+      null
+    );
+  }
+}
+
+function startCommitLifeCyclesTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    effectCountInCurrentCommit = 0;
+    beginMark("(Calling Lifecycle Methods)");
+  }
+}
+
+function stopCommitLifeCyclesTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    var count = effectCountInCurrentCommit;
+    effectCountInCurrentCommit = 0;
+    endMark(
+      "(Calling Lifecycle Methods: " + count + " Total)",
+      "(Calling Lifecycle Methods)",
+      null
+    );
+  }
+}
+
 var didWarnUpdateInsideUpdate = void 0;
 
 {
@@ -6172,12 +5847,20 @@ function callGetDerivedStateFromCatch(ctor, capturedValues) {
 }
 
 var ReactFiberClassComponent = function(
+  legacyContext,
   scheduleWork,
   computeExpirationForFiber,
   memoizeProps,
   memoizeState
 ) {
+  var cacheContext = legacyContext.cacheContext,
+    getMaskedContext = legacyContext.getMaskedContext,
+    getUnmaskedContext = legacyContext.getUnmaskedContext,
+    isContextConsumer = legacyContext.isContextConsumer,
+    hasContextChanged = legacyContext.hasContextChanged;
+
   // Class component state updater
+
   var updater = {
     isMounted: isMounted,
     enqueueSetState: function(instance, partialState, callback) {
@@ -8325,71 +8008,6 @@ function cloneChildFibers(current, workInProgress) {
   newChild.sibling = null;
 }
 
-var changedBitsStack = [];
-var currentValueStack = [];
-var stack = [];
-var index$1 = -1;
-
-var rendererSigil = void 0;
-{
-  // Use this to detect multiple renderers using the same context
-  rendererSigil = {};
-}
-
-function pushProvider(providerFiber) {
-  var context = providerFiber.type.context;
-  index$1 += 1;
-  changedBitsStack[index$1] = context._changedBits;
-  currentValueStack[index$1] = context._currentValue;
-  stack[index$1] = providerFiber;
-  context._currentValue = providerFiber.pendingProps.value;
-  context._changedBits = providerFiber.stateNode;
-
-  {
-    warning(
-      context._currentRenderer === null ||
-        context._currentRenderer === rendererSigil,
-      "Detected multiple renderers concurrently rendering the " +
-        "same context provider. This is currently unsupported."
-    );
-    context._currentRenderer = rendererSigil;
-  }
-}
-
-function popProvider(providerFiber) {
-  {
-    warning(
-      index$1 > -1 && providerFiber === stack[index$1],
-      "Unexpected pop."
-    );
-  }
-  var changedBits = changedBitsStack[index$1];
-  var currentValue = currentValueStack[index$1];
-  changedBitsStack[index$1] = null;
-  currentValueStack[index$1] = null;
-  stack[index$1] = null;
-  index$1 -= 1;
-  var context = providerFiber.type.context;
-  context._currentValue = currentValue;
-  context._changedBits = changedBits;
-}
-
-function resetProviderStack() {
-  for (var i = index$1; i > -1; i--) {
-    var providerFiber = stack[i];
-    var context = providerFiber.type.context;
-    context._currentValue = context._defaultValue;
-    context._changedBits = 0;
-    changedBitsStack[i] = null;
-    currentValueStack[i] = null;
-    stack[i] = null;
-    {
-      context._currentRenderer = null;
-    }
-  }
-  index$1 = -1;
-}
-
 var didWarnAboutBadClass = void 0;
 var didWarnAboutGetDerivedStateOnFunctionalComponent = void 0;
 var didWarnAboutStatelessRefs = void 0;
@@ -8403,6 +8021,8 @@ var didWarnAboutStatelessRefs = void 0;
 var ReactFiberBeginWork = function(
   config,
   hostContext,
+  legacyContext,
+  newContext,
   hydrationContext,
   scheduleWork,
   computeExpirationForFiber
@@ -8411,12 +8031,20 @@ var ReactFiberBeginWork = function(
     shouldDeprioritizeSubtree = config.shouldDeprioritizeSubtree;
   var pushHostContext = hostContext.pushHostContext,
     pushHostContainer = hostContext.pushHostContainer;
+  var pushProvider = newContext.pushProvider;
+  var getMaskedContext = legacyContext.getMaskedContext,
+    getUnmaskedContext = legacyContext.getUnmaskedContext,
+    hasLegacyContextChanged = legacyContext.hasContextChanged,
+    pushLegacyContextProvider = legacyContext.pushContextProvider,
+    pushTopLevelContextObject = legacyContext.pushTopLevelContextObject,
+    invalidateContextProvider = legacyContext.invalidateContextProvider;
   var enterHydrationState = hydrationContext.enterHydrationState,
     resetHydrationState = hydrationContext.resetHydrationState,
     tryToClaimNextHydratableInstance =
       hydrationContext.tryToClaimNextHydratableInstance;
 
   var _ReactFiberClassCompo = ReactFiberClassComponent(
+      legacyContext,
       scheduleWork,
       computeExpirationForFiber,
       memoizeProps,
@@ -8484,7 +8112,7 @@ var ReactFiberBeginWork = function(
 
   function updateFragment(current, workInProgress) {
     var nextChildren = workInProgress.pendingProps;
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (workInProgress.memoizedProps === nextChildren) {
@@ -8497,7 +8125,7 @@ var ReactFiberBeginWork = function(
 
   function updateMode(current, workInProgress) {
     var nextChildren = workInProgress.pendingProps.children;
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (
@@ -8526,7 +8154,7 @@ var ReactFiberBeginWork = function(
     var fn = workInProgress.type;
     var nextProps = workInProgress.pendingProps;
 
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else {
@@ -8559,7 +8187,7 @@ var ReactFiberBeginWork = function(
     // Push context providers early to prevent context stack mismatches.
     // During mounting we don't know the child context yet as the instance doesn't exist.
     // We will invalidate the child context in finishClassComponent() right after rendering.
-    var hasContext = pushContextProvider(workInProgress);
+    var hasContext = pushLegacyContextProvider(workInProgress);
     var shouldUpdate = void 0;
     if (current === null) {
       if (workInProgress.stateNode === null) {
@@ -8784,7 +8412,7 @@ var ReactFiberBeginWork = function(
     var nextProps = workInProgress.pendingProps;
     var prevProps = current !== null ? current.memoizedProps : null;
 
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (memoizedProps === nextProps) {
@@ -8919,7 +8547,7 @@ var ReactFiberBeginWork = function(
       // Push context providers early to prevent context stack mismatches.
       // During mounting we don't know the child context yet as the instance doesn't exist.
       // We will invalidate the child context in finishClassComponent() right after rendering.
-      var hasContext = pushContextProvider(workInProgress);
+      var hasContext = pushLegacyContextProvider(workInProgress);
       adoptClassInstance(workInProgress, value);
       mountClassInstance(workInProgress, renderExpirationTime);
       return finishClassComponent(
@@ -8992,7 +8620,7 @@ var ReactFiberBeginWork = function(
 
   function updateCallComponent(current, workInProgress, renderExpirationTime) {
     var nextProps = workInProgress.pendingProps;
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (workInProgress.memoizedProps === nextProps) {
@@ -9035,7 +8663,7 @@ var ReactFiberBeginWork = function(
   ) {
     pushHostContainer(workInProgress, workInProgress.stateNode.containerInfo);
     var nextChildren = workInProgress.pendingProps;
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (workInProgress.memoizedProps === nextChildren) {
@@ -9069,6 +8697,10 @@ var ReactFiberBeginWork = function(
     renderExpirationTime
   ) {
     var fiber = workInProgress.child;
+    if (fiber !== null) {
+      // Set the return pointer of the child to the work-in-progress fiber.
+      fiber["return"] = workInProgress;
+    }
     while (fiber !== null) {
       var nextFiber = void 0;
       // Visit this fiber.
@@ -9161,7 +8793,7 @@ var ReactFiberBeginWork = function(
     var newProps = workInProgress.pendingProps;
     var oldProps = workInProgress.memoizedProps;
 
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (oldProps === newProps) {
@@ -9257,7 +8889,7 @@ var ReactFiberBeginWork = function(
     var newValue = context._currentValue;
     var changedBits = context._changedBits;
 
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (changedBits === 0 && oldProps === newProps) {
@@ -9354,7 +8986,7 @@ var ReactFiberBeginWork = function(
         pushHostRootContext(workInProgress);
         break;
       case ClassComponent:
-        pushContextProvider(workInProgress);
+        pushLegacyContextProvider(workInProgress);
         break;
       case HostPortal:
         pushHostContainer(
@@ -9467,7 +9099,13 @@ var ReactFiberBeginWork = function(
   };
 };
 
-var ReactFiberCompleteWork = function(config, hostContext, hydrationContext) {
+var ReactFiberCompleteWork = function(
+  config,
+  hostContext,
+  legacyContext,
+  newContext,
+  hydrationContext
+) {
   var createInstance = config.createInstance,
     createTextInstance = config.createTextInstance,
     appendInitialChild = config.appendInitialChild,
@@ -9479,6 +9117,9 @@ var ReactFiberCompleteWork = function(config, hostContext, hydrationContext) {
     popHostContext = hostContext.popHostContext,
     getHostContext = hostContext.getHostContext,
     popHostContainer = hostContext.popHostContainer;
+  var popLegacyContextProvider = legacyContext.popContextProvider,
+    popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject;
+  var popProvider = newContext.popProvider;
   var prepareToHydrateHostInstance =
       hydrationContext.prepareToHydrateHostInstance,
     prepareToHydrateHostTextInstance =
@@ -9794,7 +9435,7 @@ var ReactFiberCompleteWork = function(config, hostContext, hydrationContext) {
         return null;
       case ClassComponent: {
         // We are leaving this subtree, so pop context if any.
-        popContextProvider(workInProgress);
+        popLegacyContextProvider(workInProgress);
 
         // If this component caught an error, schedule an error log effect.
         var instance = workInProgress.stateNode;
@@ -9813,7 +9454,7 @@ var ReactFiberCompleteWork = function(config, hostContext, hydrationContext) {
       }
       case HostRoot: {
         popHostContainer(workInProgress);
-        popTopLevelContextObject(workInProgress);
+        popTopLevelLegacyContextObject(workInProgress);
         var fiberRoot = workInProgress.stateNode;
         if (fiberRoot.pendingContext) {
           fiberRoot.context = fiberRoot.pendingContext;
@@ -10040,11 +9681,16 @@ function createCapturedValue(value, source) {
 
 var ReactFiberUnwindWork = function(
   hostContext,
+  legacyContext,
+  newContext,
   scheduleWork,
   isAlreadyFailedLegacyErrorBoundary
 ) {
   var popHostContainer = hostContext.popHostContainer,
     popHostContext = hostContext.popHostContext;
+  var popLegacyContextProvider = legacyContext.popContextProvider,
+    popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject;
+  var popProvider = newContext.popProvider;
 
   function throwException(returnFiber, sourceFiber, rawValue) {
     // The source fiber did not complete.
@@ -10100,7 +9746,7 @@ var ReactFiberUnwindWork = function(
   function unwindWork(workInProgress) {
     switch (workInProgress.tag) {
       case ClassComponent: {
-        popContextProvider(workInProgress);
+        popLegacyContextProvider(workInProgress);
         var effectTag = workInProgress.effectTag;
         if (effectTag & ShouldCapture) {
           workInProgress.effectTag = (effectTag & ~ShouldCapture) | DidCapture;
@@ -10110,7 +9756,7 @@ var ReactFiberUnwindWork = function(
       }
       case HostRoot: {
         popHostContainer(workInProgress);
-        popTopLevelContextObject(workInProgress);
+        popTopLevelLegacyContextObject(workInProgress);
         var _effectTag = workInProgress.effectTag;
         if (_effectTag & ShouldCapture) {
           workInProgress.effectTag = (_effectTag & ~ShouldCapture) | DidCapture;
@@ -10132,9 +9778,37 @@ var ReactFiberUnwindWork = function(
         return null;
     }
   }
+
+  function unwindInterruptedWork(interruptedWork) {
+    switch (interruptedWork.tag) {
+      case ClassComponent: {
+        popLegacyContextProvider(interruptedWork);
+        break;
+      }
+      case HostRoot: {
+        popHostContainer(interruptedWork);
+        popTopLevelLegacyContextObject(interruptedWork);
+        break;
+      }
+      case HostComponent: {
+        popHostContext(interruptedWork);
+        break;
+      }
+      case HostPortal:
+        popHostContainer(interruptedWork);
+        break;
+      case ContextProvider:
+        popProvider(interruptedWork);
+        break;
+      default:
+        break;
+    }
+  }
+
   return {
     throwException: throwException,
-    unwindWork: unwindWork
+    unwindWork: unwindWork,
+    unwindInterruptedWork: unwindInterruptedWork
   };
 };
 
@@ -10466,7 +10140,7 @@ var ReactFiberCommitWork = function(
             warning(
               false,
               "Unexpected ref object provided for %s. " +
-                "Use either a ref-setter function or Reacte.createRef().%s",
+                "Use either a ref-setter function or React.createRef().%s",
               getComponentName(finishedWork),
               getStackAddendumByWorkInProgressFiber(finishedWork)
             );
@@ -10972,9 +10646,12 @@ var ReactFiberCommitWork = function(
 
 var NO_CONTEXT = {};
 
-var ReactFiberHostContext = function(config) {
+var ReactFiberHostContext = function(config, stack) {
   var getChildHostContext = config.getChildHostContext,
     getRootHostContext = config.getRootHostContext;
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop;
 
   var contextStackCursor = createCursor(NO_CONTEXT);
   var contextFiberStackCursor = createCursor(NO_CONTEXT);
@@ -11045,19 +10722,13 @@ var ReactFiberHostContext = function(config) {
     pop(contextFiberStackCursor, fiber);
   }
 
-  function resetHostContainer() {
-    contextStackCursor.current = NO_CONTEXT;
-    rootInstanceStackCursor.current = NO_CONTEXT;
-  }
-
   return {
     getHostContext: getHostContext,
     getRootHostContainer: getRootHostContainer,
     popHostContainer: popHostContainer,
     popHostContext: popHostContext,
     pushHostContainer: pushHostContainer,
-    pushHostContext: pushHostContext,
-    resetHostContainer: resetHostContainer
+    pushHostContext: pushHostContext
   };
 };
 
@@ -11427,6 +11098,425 @@ var ReactFiberInstrumentation = {
 
 var ReactFiberInstrumentation_1 = ReactFiberInstrumentation;
 
+var warnedAboutMissingGetChildContext = void 0;
+
+{
+  warnedAboutMissingGetChildContext = {};
+}
+
+var ReactFiberLegacyContext = function(stack) {
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop;
+
+  // A cursor to the current merged context object on the stack.
+
+  var contextStackCursor = createCursor(emptyObject);
+  // A cursor to a boolean indicating whether the context has changed.
+  var didPerformWorkStackCursor = createCursor(false);
+  // Keep track of the previous context object that was on the stack.
+  // We use this to get access to the parent context after we have already
+  // pushed the next context provider, and now need to merge their contexts.
+  var previousContext = emptyObject;
+
+  function getUnmaskedContext(workInProgress) {
+    var hasOwnContext = isContextProvider(workInProgress);
+    if (hasOwnContext) {
+      // If the fiber is a context provider itself, when we read its context
+      // we have already pushed its own child context on the stack. A context
+      // provider should not "see" its own child context. Therefore we read the
+      // previous (parent) context instead for a context provider.
+      return previousContext;
+    }
+    return contextStackCursor.current;
+  }
+
+  function cacheContext(workInProgress, unmaskedContext, maskedContext) {
+    var instance = workInProgress.stateNode;
+    instance.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext;
+    instance.__reactInternalMemoizedMaskedChildContext = maskedContext;
+  }
+
+  function getMaskedContext(workInProgress, unmaskedContext) {
+    var type = workInProgress.type;
+    var contextTypes = type.contextTypes;
+    if (!contextTypes) {
+      return emptyObject;
+    }
+
+    // Avoid recreating masked context unless unmasked context has changed.
+    // Failing to do this will result in unnecessary calls to componentWillReceiveProps.
+    // This may trigger infinite loops if componentWillReceiveProps calls setState.
+    var instance = workInProgress.stateNode;
+    if (
+      instance &&
+      instance.__reactInternalMemoizedUnmaskedChildContext === unmaskedContext
+    ) {
+      return instance.__reactInternalMemoizedMaskedChildContext;
+    }
+
+    var context = {};
+    for (var key in contextTypes) {
+      context[key] = unmaskedContext[key];
+    }
+
+    {
+      var name = getComponentName(workInProgress) || "Unknown";
+      checkPropTypes(
+        contextTypes,
+        context,
+        "context",
+        name,
+        ReactDebugCurrentFiber.getCurrentFiberStackAddendum
+      );
+    }
+
+    // Cache unmasked context so we can avoid recreating masked context unless necessary.
+    // Context is created before the class component is instantiated so check for instance.
+    if (instance) {
+      cacheContext(workInProgress, unmaskedContext, context);
+    }
+
+    return context;
+  }
+
+  function hasContextChanged() {
+    return didPerformWorkStackCursor.current;
+  }
+
+  function isContextConsumer(fiber) {
+    return fiber.tag === ClassComponent && fiber.type.contextTypes != null;
+  }
+
+  function isContextProvider(fiber) {
+    return fiber.tag === ClassComponent && fiber.type.childContextTypes != null;
+  }
+
+  function popContextProvider(fiber) {
+    if (!isContextProvider(fiber)) {
+      return;
+    }
+
+    pop(didPerformWorkStackCursor, fiber);
+    pop(contextStackCursor, fiber);
+  }
+
+  function popTopLevelContextObject(fiber) {
+    pop(didPerformWorkStackCursor, fiber);
+    pop(contextStackCursor, fiber);
+  }
+
+  function pushTopLevelContextObject(fiber, context, didChange) {
+    invariant(
+      contextStackCursor.cursor == null,
+      "Unexpected context found on stack. " +
+        "This error is likely caused by a bug in React. Please file an issue."
+    );
+
+    push(contextStackCursor, context, fiber);
+    push(didPerformWorkStackCursor, didChange, fiber);
+  }
+
+  function processChildContext(fiber, parentContext) {
+    var instance = fiber.stateNode;
+    var childContextTypes = fiber.type.childContextTypes;
+
+    // TODO (bvaughn) Replace this behavior with an invariant() in the future.
+    // It has only been added in Fiber to match the (unintentional) behavior in Stack.
+    if (typeof instance.getChildContext !== "function") {
+      {
+        var componentName = getComponentName(fiber) || "Unknown";
+
+        if (!warnedAboutMissingGetChildContext[componentName]) {
+          warnedAboutMissingGetChildContext[componentName] = true;
+          warning(
+            false,
+            "%s.childContextTypes is specified but there is no getChildContext() method " +
+              "on the instance. You can either define getChildContext() on %s or remove " +
+              "childContextTypes from it.",
+            componentName,
+            componentName
+          );
+        }
+      }
+      return parentContext;
+    }
+
+    var childContext = void 0;
+    {
+      ReactDebugCurrentFiber.setCurrentPhase("getChildContext");
+    }
+    startPhaseTimer(fiber, "getChildContext");
+    childContext = instance.getChildContext();
+    stopPhaseTimer();
+    {
+      ReactDebugCurrentFiber.setCurrentPhase(null);
+    }
+    for (var contextKey in childContext) {
+      invariant(
+        contextKey in childContextTypes,
+        '%s.getChildContext(): key "%s" is not defined in childContextTypes.',
+        getComponentName(fiber) || "Unknown",
+        contextKey
+      );
+    }
+    {
+      var name = getComponentName(fiber) || "Unknown";
+      checkPropTypes(
+        childContextTypes,
+        childContext,
+        "child context",
+        name,
+        // In practice, there is one case in which we won't get a stack. It's when
+        // somebody calls unstable_renderSubtreeIntoContainer() and we process
+        // context from the parent component instance. The stack will be missing
+        // because it's outside of the reconciliation, and so the pointer has not
+        // been set. This is rare and doesn't matter. We'll also remove that API.
+        ReactDebugCurrentFiber.getCurrentFiberStackAddendum
+      );
+    }
+
+    return Object.assign({}, parentContext, childContext);
+  }
+
+  function pushContextProvider(workInProgress) {
+    if (!isContextProvider(workInProgress)) {
+      return false;
+    }
+
+    var instance = workInProgress.stateNode;
+    // We push the context as early as possible to ensure stack integrity.
+    // If the instance does not exist yet, we will push null at first,
+    // and replace it on the stack later when invalidating the context.
+    var memoizedMergedChildContext =
+      (instance && instance.__reactInternalMemoizedMergedChildContext) ||
+      emptyObject;
+
+    // Remember the parent context so we can merge with it later.
+    // Inherit the parent's did-perform-work value to avoid inadvertently blocking updates.
+    previousContext = contextStackCursor.current;
+    push(contextStackCursor, memoizedMergedChildContext, workInProgress);
+    push(
+      didPerformWorkStackCursor,
+      didPerformWorkStackCursor.current,
+      workInProgress
+    );
+
+    return true;
+  }
+
+  function invalidateContextProvider(workInProgress, didChange) {
+    var instance = workInProgress.stateNode;
+    invariant(
+      instance,
+      "Expected to have an instance by this point. " +
+        "This error is likely caused by a bug in React. Please file an issue."
+    );
+
+    if (didChange) {
+      // Merge parent and own context.
+      // Skip this if we're not updating due to sCU.
+      // This avoids unnecessarily recomputing memoized values.
+      var mergedContext = processChildContext(workInProgress, previousContext);
+      instance.__reactInternalMemoizedMergedChildContext = mergedContext;
+
+      // Replace the old (or empty) context with the new one.
+      // It is important to unwind the context in the reverse order.
+      pop(didPerformWorkStackCursor, workInProgress);
+      pop(contextStackCursor, workInProgress);
+      // Now push the new context and mark that it has changed.
+      push(contextStackCursor, mergedContext, workInProgress);
+      push(didPerformWorkStackCursor, didChange, workInProgress);
+    } else {
+      pop(didPerformWorkStackCursor, workInProgress);
+      push(didPerformWorkStackCursor, didChange, workInProgress);
+    }
+  }
+
+  function findCurrentUnmaskedContext(fiber) {
+    // Currently this is only used with renderSubtreeIntoContainer; not sure if it
+    // makes sense elsewhere
+    invariant(
+      isFiberMounted(fiber) && fiber.tag === ClassComponent,
+      "Expected subtree parent to be a mounted class component. " +
+        "This error is likely caused by a bug in React. Please file an issue."
+    );
+
+    var node = fiber;
+    while (node.tag !== HostRoot) {
+      if (isContextProvider(node)) {
+        return node.stateNode.__reactInternalMemoizedMergedChildContext;
+      }
+      var parent = node["return"];
+      invariant(
+        parent,
+        "Found unexpected detached subtree parent. " +
+          "This error is likely caused by a bug in React. Please file an issue."
+      );
+      node = parent;
+    }
+    return node.stateNode.context;
+  }
+
+  return {
+    getUnmaskedContext: getUnmaskedContext,
+    cacheContext: cacheContext,
+    getMaskedContext: getMaskedContext,
+    hasContextChanged: hasContextChanged,
+    isContextConsumer: isContextConsumer,
+    isContextProvider: isContextProvider,
+    popContextProvider: popContextProvider,
+    popTopLevelContextObject: popTopLevelContextObject,
+    pushTopLevelContextObject: pushTopLevelContextObject,
+    processChildContext: processChildContext,
+    pushContextProvider: pushContextProvider,
+    invalidateContextProvider: invalidateContextProvider,
+    findCurrentUnmaskedContext: findCurrentUnmaskedContext
+  };
+};
+
+var ReactFiberNewContext = function(stack) {
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop;
+
+  var providerCursor = createCursor(null);
+  var valueCursor = createCursor(null);
+  var changedBitsCursor = createCursor(0);
+
+  var rendererSigil = void 0;
+  {
+    // Use this to detect multiple renderers using the same context
+    rendererSigil = {};
+  }
+
+  function pushProvider(providerFiber) {
+    var context = providerFiber.type.context;
+
+    push(changedBitsCursor, context._changedBits, providerFiber);
+    push(valueCursor, context._currentValue, providerFiber);
+    push(providerCursor, providerFiber, providerFiber);
+
+    context._currentValue = providerFiber.pendingProps.value;
+    context._changedBits = providerFiber.stateNode;
+
+    {
+      warning(
+        context._currentRenderer === null ||
+          context._currentRenderer === rendererSigil,
+        "Detected multiple renderers concurrently rendering the " +
+          "same context provider. This is currently unsupported."
+      );
+      context._currentRenderer = rendererSigil;
+    }
+  }
+
+  function popProvider(providerFiber) {
+    var changedBits = changedBitsCursor.current;
+    var currentValue = valueCursor.current;
+
+    pop(providerCursor, providerFiber);
+    pop(valueCursor, providerFiber);
+    pop(changedBitsCursor, providerFiber);
+
+    var context = providerFiber.type.context;
+    context._currentValue = currentValue;
+    context._changedBits = changedBits;
+  }
+
+  return {
+    pushProvider: pushProvider,
+    popProvider: popProvider
+  };
+};
+
+var ReactFiberStack = function() {
+  var valueStack = [];
+
+  var fiberStack = void 0;
+
+  {
+    fiberStack = [];
+  }
+
+  var index = -1;
+
+  function createCursor(defaultValue) {
+    return {
+      current: defaultValue
+    };
+  }
+
+  function isEmpty() {
+    return index === -1;
+  }
+
+  function pop(cursor, fiber) {
+    if (index < 0) {
+      {
+        warning(false, "Unexpected pop.");
+      }
+      return;
+    }
+
+    {
+      if (fiber !== fiberStack[index]) {
+        warning(false, "Unexpected Fiber popped.");
+      }
+    }
+
+    cursor.current = valueStack[index];
+
+    valueStack[index] = null;
+
+    {
+      fiberStack[index] = null;
+    }
+
+    index--;
+  }
+
+  function push(cursor, value, fiber) {
+    index++;
+
+    valueStack[index] = cursor.current;
+
+    {
+      fiberStack[index] = fiber;
+    }
+
+    cursor.current = value;
+  }
+
+  function checkThatStackIsEmpty() {
+    {
+      if (index !== -1) {
+        warning(
+          false,
+          "Expected an empty stack. Something was not reset properly."
+        );
+      }
+    }
+  }
+
+  function resetStackAfterFatalErrorInDev() {
+    {
+      index = -1;
+      valueStack.length = 0;
+      fiberStack.length = 0;
+    }
+  }
+
+  return {
+    createCursor: createCursor,
+    isEmpty: isEmpty,
+    pop: pop,
+    push: push,
+    checkThatStackIsEmpty: checkThatStackIsEmpty,
+    resetStackAfterFatalErrorInDev: resetStackAfterFatalErrorInDev
+  };
+};
+
 var invokeGuardedCallback$2 = ReactErrorUtils.invokeGuardedCallback;
 var hasCaughtError = ReactErrorUtils.hasCaughtError;
 var clearCaughtError = ReactErrorUtils.clearCaughtError;
@@ -11487,16 +11577,23 @@ var warnAboutInvalidUpdates = void 0;
 }
 
 var ReactFiberScheduler = function(config) {
-  var hostContext = ReactFiberHostContext(config);
+  var stack = ReactFiberStack();
+  var hostContext = ReactFiberHostContext(config, stack);
+  var legacyContext = ReactFiberLegacyContext(stack);
+  var newContext = ReactFiberNewContext(stack);
   var popHostContext = hostContext.popHostContext,
     popHostContainer = hostContext.popHostContainer;
+  var popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject,
+    popLegacyContextProvider = legacyContext.popContextProvider;
+  var popProvider = newContext.popProvider;
 
   var hydrationContext = ReactFiberHydrationContext(config);
-  var resetHostContainer = hostContext.resetHostContainer;
 
   var _ReactFiberBeginWork = ReactFiberBeginWork(
       config,
       hostContext,
+      legacyContext,
+      newContext,
       hydrationContext,
       scheduleWork,
       computeExpirationForFiber
@@ -11506,17 +11603,22 @@ var ReactFiberScheduler = function(config) {
   var _ReactFiberCompleteWo = ReactFiberCompleteWork(
       config,
       hostContext,
+      legacyContext,
+      newContext,
       hydrationContext
     ),
     completeWork = _ReactFiberCompleteWo.completeWork;
 
   var _ReactFiberUnwindWork = ReactFiberUnwindWork(
       hostContext,
+      legacyContext,
+      newContext,
       scheduleWork,
       isAlreadyFailedLegacyErrorBoundary
     ),
     throwException = _ReactFiberUnwindWork.throwException,
-    unwindWork = _ReactFiberUnwindWork.unwindWork;
+    unwindWork = _ReactFiberUnwindWork.unwindWork,
+    unwindInterruptedWork = _ReactFiberUnwindWork.unwindInterruptedWork;
 
   var _ReactFiberCommitWork = ReactFiberCommitWork(
       config,
@@ -11585,13 +11687,13 @@ var ReactFiberScheduler = function(config) {
       switch (failedUnitOfWork.tag) {
         case HostRoot:
           popHostContainer(failedUnitOfWork);
-          popTopLevelContextObject(failedUnitOfWork);
+          popTopLevelLegacyContextObject(failedUnitOfWork);
           break;
         case HostComponent:
           popHostContext(failedUnitOfWork);
           break;
         case ClassComponent:
-          popContextProvider(failedUnitOfWork);
+          popLegacyContextProvider(failedUnitOfWork);
           break;
         case HostPortal:
           popHostContainer(failedUnitOfWork);
@@ -11611,18 +11713,18 @@ var ReactFiberScheduler = function(config) {
     };
   }
 
-  function resetContextStack() {
-    // Reset the stack
-    reset();
-    // Reset the cursors
-    resetContext();
-    resetHostContainer();
-
-    // TODO: Unify new context implementation with other stacks
-    resetProviderStack();
+  function resetStack() {
+    if (nextUnitOfWork !== null) {
+      var interruptedWork = nextUnitOfWork["return"];
+      while (interruptedWork !== null) {
+        unwindInterruptedWork(interruptedWork);
+        interruptedWork = interruptedWork["return"];
+      }
+    }
 
     {
       ReactStrictModeWarnings.discardPendingWarnings();
+      stack.checkThatStackIsEmpty();
     }
 
     nextRoot = null;
@@ -12146,7 +12248,7 @@ var ReactFiberScheduler = function(config) {
       nextUnitOfWork === null
     ) {
       // Reset the stack and start working from the root.
-      resetContextStack();
+      resetStack();
       nextRoot = root;
       nextRenderExpirationTime = expirationTime;
       nextUnitOfWork = createWorkInProgress(
@@ -12199,6 +12301,9 @@ var ReactFiberScheduler = function(config) {
     // Yield back to main thread.
     if (didFatal) {
       // There was a fatal error.
+      {
+        stack.resetStackAfterFatalErrorInDev();
+      }
       return null;
     } else if (nextUnitOfWork === null) {
       // We reached the root.
@@ -12399,7 +12504,7 @@ var ReactFiberScheduler = function(config) {
           ) {
             // This is an interruption. (Used for performance tracking.)
             interruptedBy = fiber;
-            resetContextStack();
+            resetStack();
           }
           if (nextRoot !== root || !isWorking) {
             requestWork(root, expirationTime);
@@ -12970,7 +13075,8 @@ var ReactFiberScheduler = function(config) {
     syncUpdates: syncUpdates,
     interactiveUpdates: interactiveUpdates,
     flushInteractiveUpdates: flushInteractiveUpdates,
-    computeUniqueAsyncExpiration: computeUniqueAsyncExpiration
+    computeUniqueAsyncExpiration: computeUniqueAsyncExpiration,
+    legacyContext: legacyContext
   };
 };
 
@@ -12983,18 +13089,6 @@ var didWarnAboutNestedUpdates = void 0;
 // 0 is PROD, 1 is DEV.
 // Might add PROFILE later.
 
-function getContextForSubtree(parentComponent) {
-  if (!parentComponent) {
-    return emptyObject;
-  }
-
-  var fiber = get(parentComponent);
-  var parentContext = findCurrentUnmaskedContext(fiber);
-  return isContextProvider(fiber)
-    ? processChildContext(fiber, parentContext)
-    : parentContext;
-}
-
 var ReactFiberReconciler$1 = function(config) {
   var getPublicInstance = config.getPublicInstance;
 
@@ -13013,7 +13107,24 @@ var ReactFiberReconciler$1 = function(config) {
     deferredUpdates = _ReactFiberScheduler.deferredUpdates,
     syncUpdates = _ReactFiberScheduler.syncUpdates,
     interactiveUpdates = _ReactFiberScheduler.interactiveUpdates,
-    flushInteractiveUpdates = _ReactFiberScheduler.flushInteractiveUpdates;
+    flushInteractiveUpdates = _ReactFiberScheduler.flushInteractiveUpdates,
+    legacyContext = _ReactFiberScheduler.legacyContext;
+
+  var findCurrentUnmaskedContext = legacyContext.findCurrentUnmaskedContext,
+    isContextProvider = legacyContext.isContextProvider,
+    processChildContext = legacyContext.processChildContext;
+
+  function getContextForSubtree(parentComponent) {
+    if (!parentComponent) {
+      return emptyObject;
+    }
+
+    var fiber = get(parentComponent);
+    var parentContext = findCurrentUnmaskedContext(fiber);
+    return isContextProvider(fiber)
+      ? processChildContext(fiber, parentContext)
+      : parentContext;
+  }
 
   function scheduleRootUpdate(
     current,
diff --git a/Libraries/Renderer/ReactFabric-prod.js b/Libraries/Renderer/ReactFabric-prod.js
index 637481f04..08f112c70 100644
--- a/Libraries/Renderer/ReactFabric-prod.js
+++ b/Libraries/Renderer/ReactFabric-prod.js
@@ -1633,136 +1633,6 @@ function findCurrentHostFiberWithNoPortals(parent) {
   }
   return null;
 }
-var valueStack = [],
-  index = -1;
-function pop(cursor) {
-  0 > index ||
-    ((cursor.current = valueStack[index]), (valueStack[index] = null), index--);
-}
-function push(cursor, value) {
-  index++;
-  valueStack[index] = cursor.current;
-  cursor.current = value;
-}
-function getStackAddendumByWorkInProgressFiber(workInProgress) {
-  var info = "";
-  do {
-    a: switch (workInProgress.tag) {
-      case 0:
-      case 1:
-      case 2:
-      case 5:
-        var owner = workInProgress._debugOwner,
-          source = workInProgress._debugSource;
-        var JSCompiler_inline_result = getComponentName(workInProgress);
-        var ownerName = null;
-        owner && (ownerName = getComponentName(owner));
-        owner = source;
-        JSCompiler_inline_result =
-          "\n    in " +
-          (JSCompiler_inline_result || "Unknown") +
-          (owner
-            ? " (at " +
-              owner.fileName.replace(/^.*[\\\/]/, "") +
-              ":" +
-              owner.lineNumber +
-              ")"
-            : ownerName ? " (created by " + ownerName + ")" : "");
-        break a;
-      default:
-        JSCompiler_inline_result = "";
-    }
-    info += JSCompiler_inline_result;
-    workInProgress = workInProgress["return"];
-  } while (workInProgress);
-  return info;
-}
-new Set();
-var contextStackCursor = { current: emptyObject },
-  didPerformWorkStackCursor = { current: !1 },
-  previousContext = emptyObject;
-function getUnmaskedContext(workInProgress) {
-  return isContextProvider(workInProgress)
-    ? previousContext
-    : contextStackCursor.current;
-}
-function getMaskedContext(workInProgress, unmaskedContext) {
-  var contextTypes = workInProgress.type.contextTypes;
-  if (!contextTypes) return emptyObject;
-  var instance = workInProgress.stateNode;
-  if (
-    instance &&
-    instance.__reactInternalMemoizedUnmaskedChildContext === unmaskedContext
-  )
-    return instance.__reactInternalMemoizedMaskedChildContext;
-  var context = {},
-    key;
-  for (key in contextTypes) context[key] = unmaskedContext[key];
-  instance &&
-    ((workInProgress = workInProgress.stateNode),
-    (workInProgress.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext),
-    (workInProgress.__reactInternalMemoizedMaskedChildContext = context));
-  return context;
-}
-function isContextProvider(fiber) {
-  return 2 === fiber.tag && null != fiber.type.childContextTypes;
-}
-function popContextProvider(fiber) {
-  isContextProvider(fiber) &&
-    (pop(didPerformWorkStackCursor, fiber), pop(contextStackCursor, fiber));
-}
-function pushTopLevelContextObject(fiber, context, didChange) {
-  invariant(
-    null == contextStackCursor.cursor,
-    "Unexpected context found on stack. This error is likely caused by a bug in React. Please file an issue."
-  );
-  push(contextStackCursor, context, fiber);
-  push(didPerformWorkStackCursor, didChange, fiber);
-}
-function processChildContext(fiber, parentContext) {
-  var instance = fiber.stateNode,
-    childContextTypes = fiber.type.childContextTypes;
-  if ("function" !== typeof instance.getChildContext) return parentContext;
-  instance = instance.getChildContext();
-  for (var contextKey in instance)
-    invariant(
-      contextKey in childContextTypes,
-      '%s.getChildContext(): key "%s" is not defined in childContextTypes.',
-      getComponentName(fiber) || "Unknown",
-      contextKey
-    );
-  return Object.assign({}, parentContext, instance);
-}
-function pushContextProvider(workInProgress) {
-  if (!isContextProvider(workInProgress)) return !1;
-  var instance = workInProgress.stateNode;
-  instance =
-    (instance && instance.__reactInternalMemoizedMergedChildContext) ||
-    emptyObject;
-  previousContext = contextStackCursor.current;
-  push(contextStackCursor, instance, workInProgress);
-  push(
-    didPerformWorkStackCursor,
-    didPerformWorkStackCursor.current,
-    workInProgress
-  );
-  return !0;
-}
-function invalidateContextProvider(workInProgress, didChange) {
-  var instance = workInProgress.stateNode;
-  invariant(
-    instance,
-    "Expected to have an instance by this point. This error is likely caused by a bug in React. Please file an issue."
-  );
-  if (didChange) {
-    var mergedContext = processChildContext(workInProgress, previousContext);
-    instance.__reactInternalMemoizedMergedChildContext = mergedContext;
-    pop(didPerformWorkStackCursor, workInProgress);
-    pop(contextStackCursor, workInProgress);
-    push(contextStackCursor, mergedContext, workInProgress);
-  } else pop(didPerformWorkStackCursor, workInProgress);
-  push(didPerformWorkStackCursor, didChange, workInProgress);
-}
 function FiberNode(tag, pendingProps, key, mode) {
   this.tag = tag;
   this.key = key;
@@ -1929,6 +1799,40 @@ function onCommitRoot(root) {
 function onCommitUnmount(fiber) {
   "function" === typeof onCommitFiberUnmount && onCommitFiberUnmount(fiber);
 }
+function getStackAddendumByWorkInProgressFiber(workInProgress) {
+  var info = "";
+  do {
+    a: switch (workInProgress.tag) {
+      case 0:
+      case 1:
+      case 2:
+      case 5:
+        var owner = workInProgress._debugOwner,
+          source = workInProgress._debugSource;
+        var JSCompiler_inline_result = getComponentName(workInProgress);
+        var ownerName = null;
+        owner && (ownerName = getComponentName(owner));
+        owner = source;
+        JSCompiler_inline_result =
+          "\n    in " +
+          (JSCompiler_inline_result || "Unknown") +
+          (owner
+            ? " (at " +
+              owner.fileName.replace(/^.*[\\\/]/, "") +
+              ":" +
+              owner.lineNumber +
+              ")"
+            : ownerName ? " (created by " + ownerName + ")" : "");
+        break a;
+      default:
+        JSCompiler_inline_result = "";
+    }
+    info += JSCompiler_inline_result;
+    workInProgress = workInProgress["return"];
+  } while (workInProgress);
+  return info;
+}
+new Set();
 function createUpdateQueue(baseState) {
   return {
     baseState: baseState,
@@ -2084,6 +1988,7 @@ function commitCallbacks(queue, context) {
     }
 }
 function ReactFiberClassComponent(
+  legacyContext,
   scheduleWork,
   computeExpirationForFiber,
   memoizeProps,
@@ -2140,62 +2045,66 @@ function ReactFiberClassComponent(
         workInProgress.memoizedState
       );
   }
-  var updater = {
-    isMounted: isMounted,
-    enqueueSetState: function(instance, partialState, callback) {
-      instance = instance._reactInternalFiber;
-      callback = void 0 === callback ? null : callback;
-      var expirationTime = computeExpirationForFiber(instance);
-      insertUpdateIntoFiber(instance, {
-        expirationTime: expirationTime,
-        partialState: partialState,
-        callback: callback,
-        isReplace: !1,
-        isForced: !1,
-        capturedValue: null,
-        next: null
-      });
-      scheduleWork(instance, expirationTime);
-    },
-    enqueueReplaceState: function(instance, state, callback) {
-      instance = instance._reactInternalFiber;
-      callback = void 0 === callback ? null : callback;
-      var expirationTime = computeExpirationForFiber(instance);
-      insertUpdateIntoFiber(instance, {
-        expirationTime: expirationTime,
-        partialState: state,
-        callback: callback,
-        isReplace: !0,
-        isForced: !1,
-        capturedValue: null,
-        next: null
-      });
-      scheduleWork(instance, expirationTime);
-    },
-    enqueueForceUpdate: function(instance, callback) {
-      instance = instance._reactInternalFiber;
-      callback = void 0 === callback ? null : callback;
-      var expirationTime = computeExpirationForFiber(instance);
-      insertUpdateIntoFiber(instance, {
-        expirationTime: expirationTime,
-        partialState: null,
-        callback: callback,
-        isReplace: !1,
-        isForced: !0,
-        capturedValue: null,
-        next: null
-      });
-      scheduleWork(instance, expirationTime);
-    }
-  };
+  var cacheContext = legacyContext.cacheContext,
+    getMaskedContext = legacyContext.getMaskedContext,
+    getUnmaskedContext = legacyContext.getUnmaskedContext,
+    isContextConsumer = legacyContext.isContextConsumer,
+    hasContextChanged = legacyContext.hasContextChanged,
+    updater = {
+      isMounted: isMounted,
+      enqueueSetState: function(instance, partialState, callback) {
+        instance = instance._reactInternalFiber;
+        callback = void 0 === callback ? null : callback;
+        var expirationTime = computeExpirationForFiber(instance);
+        insertUpdateIntoFiber(instance, {
+          expirationTime: expirationTime,
+          partialState: partialState,
+          callback: callback,
+          isReplace: !1,
+          isForced: !1,
+          capturedValue: null,
+          next: null
+        });
+        scheduleWork(instance, expirationTime);
+      },
+      enqueueReplaceState: function(instance, state, callback) {
+        instance = instance._reactInternalFiber;
+        callback = void 0 === callback ? null : callback;
+        var expirationTime = computeExpirationForFiber(instance);
+        insertUpdateIntoFiber(instance, {
+          expirationTime: expirationTime,
+          partialState: state,
+          callback: callback,
+          isReplace: !0,
+          isForced: !1,
+          capturedValue: null,
+          next: null
+        });
+        scheduleWork(instance, expirationTime);
+      },
+      enqueueForceUpdate: function(instance, callback) {
+        instance = instance._reactInternalFiber;
+        callback = void 0 === callback ? null : callback;
+        var expirationTime = computeExpirationForFiber(instance);
+        insertUpdateIntoFiber(instance, {
+          expirationTime: expirationTime,
+          partialState: null,
+          callback: callback,
+          isReplace: !1,
+          isForced: !0,
+          capturedValue: null,
+          next: null
+        });
+        scheduleWork(instance, expirationTime);
+      }
+    };
   return {
     adoptClassInstance: adoptClassInstance,
     callGetDerivedStateFromProps: callGetDerivedStateFromProps,
     constructClassInstance: function(workInProgress, props) {
       var ctor = workInProgress.type,
         unmaskedContext = getUnmaskedContext(workInProgress),
-        needsContext =
-          2 === workInProgress.tag && null != workInProgress.type.contextTypes,
+        needsContext = isContextConsumer(workInProgress),
         context = needsContext
           ? getMaskedContext(workInProgress, unmaskedContext)
           : emptyObject;
@@ -2212,10 +2121,7 @@ function ReactFiberClassComponent(
           workInProgress.memoizedState,
           props
         ));
-      needsContext &&
-        ((workInProgress = workInProgress.stateNode),
-        (workInProgress.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext),
-        (workInProgress.__reactInternalMemoizedMaskedChildContext = context));
+      needsContext && cacheContext(workInProgress, unmaskedContext, context);
       return ctor;
     },
     mountClassInstance: function(workInProgress, renderExpirationTime) {
@@ -2300,7 +2206,7 @@ function ReactFiberClassComponent(
         !(
           oldProps !== newProps ||
           oldState !== renderExpirationTime ||
-          didPerformWorkStackCursor.current ||
+          hasContextChanged() ||
           (null !== workInProgress.updateQueue &&
             workInProgress.updateQueue.hasForceUpdate)
         )
@@ -2389,7 +2295,7 @@ function ReactFiberClassComponent(
         !(
           oldProps !== newProps ||
           oldContext !== renderExpirationTime ||
-          didPerformWorkStackCursor.current ||
+          hasContextChanged() ||
           (null !== workInProgress.updateQueue &&
             workInProgress.updateQueue.hasForceUpdate)
         )
@@ -3112,34 +3018,12 @@ function ChildReconciler(shouldTrackSideEffects) {
   };
 }
 var reconcileChildFibers = ChildReconciler(!0),
-  mountChildFibers = ChildReconciler(!1),
-  changedBitsStack = [],
-  currentValueStack = [],
-  stack = [],
-  index$1 = -1;
-function pushProvider(providerFiber) {
-  var context = providerFiber.type.context;
-  index$1 += 1;
-  changedBitsStack[index$1] = context._changedBits;
-  currentValueStack[index$1] = context._currentValue;
-  stack[index$1] = providerFiber;
-  context._currentValue = providerFiber.pendingProps.value;
-  context._changedBits = providerFiber.stateNode;
-}
-function popProvider(providerFiber) {
-  var changedBits = changedBitsStack[index$1],
-    currentValue = currentValueStack[index$1];
-  changedBitsStack[index$1] = null;
-  currentValueStack[index$1] = null;
-  stack[index$1] = null;
-  --index$1;
-  providerFiber = providerFiber.type.context;
-  providerFiber._currentValue = currentValue;
-  providerFiber._changedBits = changedBits;
-}
+  mountChildFibers = ChildReconciler(!1);
 function ReactFiberBeginWork(
   config,
   hostContext,
+  legacyContext,
+  newContext,
   hydrationContext,
   scheduleWork,
   computeExpirationForFiber
@@ -3236,7 +3120,12 @@ function ReactFiberBeginWork(
     changedBits,
     renderExpirationTime
   ) {
-    for (var fiber = workInProgress.child; null !== fiber; ) {
+    var fiber = workInProgress.child;
+    for (
+      null !== fiber && (fiber["return"] = workInProgress);
+      null !== fiber;
+
+    ) {
       switch (fiber.tag) {
         case 12:
           var nextFiber = fiber.stateNode | 0;
@@ -3295,7 +3184,7 @@ function ReactFiberBeginWork(
     var context = workInProgress.type.context,
       newProps = workInProgress.pendingProps,
       oldProps = workInProgress.memoizedProps;
-    if (!didPerformWorkStackCursor.current && oldProps === newProps)
+    if (!hasLegacyContextChanged() && oldProps === newProps)
       return (
         (workInProgress.stateNode = 0),
         pushProvider(workInProgress),
@@ -3382,11 +3271,19 @@ function ReactFiberBeginWork(
     shouldDeprioritizeSubtree = config.shouldDeprioritizeSubtree,
     pushHostContext = hostContext.pushHostContext,
     pushHostContainer = hostContext.pushHostContainer,
+    pushProvider = newContext.pushProvider,
+    getMaskedContext = legacyContext.getMaskedContext,
+    getUnmaskedContext = legacyContext.getUnmaskedContext,
+    hasLegacyContextChanged = legacyContext.hasContextChanged,
+    pushLegacyContextProvider = legacyContext.pushContextProvider,
+    pushTopLevelContextObject = legacyContext.pushTopLevelContextObject,
+    invalidateContextProvider = legacyContext.invalidateContextProvider,
     enterHydrationState = hydrationContext.enterHydrationState,
     resetHydrationState = hydrationContext.resetHydrationState,
     tryToClaimNextHydratableInstance =
       hydrationContext.tryToClaimNextHydratableInstance;
   config = ReactFiberClassComponent(
+    legacyContext,
     scheduleWork,
     computeExpirationForFiber,
     function(workInProgress, nextProps) {
@@ -3413,7 +3310,7 @@ function ReactFiberBeginWork(
             pushHostRootContext(workInProgress);
             break;
           case 2:
-            pushContextProvider(workInProgress);
+            pushLegacyContextProvider(workInProgress);
             break;
           case 4:
             pushHostContainer(
@@ -3459,7 +3356,7 @@ function ReactFiberBeginWork(
                     workInProgress.memoizedState,
                     props
                   ))),
-              (props = pushContextProvider(workInProgress)),
+              (props = pushLegacyContextProvider(workInProgress)),
               adoptClassInstance(workInProgress, fn),
               mountClassInstance(workInProgress, renderExpirationTime),
               (current = finishClassComponent(
@@ -3479,7 +3376,7 @@ function ReactFiberBeginWork(
           return (
             (props = workInProgress.type),
             (renderExpirationTime = workInProgress.pendingProps),
-            didPerformWorkStackCursor.current ||
+            hasLegacyContextChanged() ||
             workInProgress.memoizedProps !== renderExpirationTime
               ? ((fn = getUnmaskedContext(workInProgress)),
                 (fn = getMaskedContext(workInProgress, fn)),
@@ -3495,7 +3392,7 @@ function ReactFiberBeginWork(
             current
           );
         case 2:
-          props = pushContextProvider(workInProgress);
+          props = pushLegacyContextProvider(workInProgress);
           null === current
             ? null === workInProgress.stateNode
               ? (constructClassInstance(
@@ -3577,7 +3474,7 @@ function ReactFiberBeginWork(
             updateQueue = workInProgress.memoizedProps;
             fn = workInProgress.pendingProps;
             unmaskedContext = null !== current ? current.memoizedProps : null;
-            if (!didPerformWorkStackCursor.current && updateQueue === fn) {
+            if (!hasLegacyContextChanged() && updateQueue === fn) {
               if (
                 (updateQueue =
                   workInProgress.mode & 1 &&
@@ -3619,7 +3516,7 @@ function ReactFiberBeginWork(
         case 7:
           return (
             (props = workInProgress.pendingProps),
-            didPerformWorkStackCursor.current ||
+            hasLegacyContextChanged() ||
               workInProgress.memoizedProps !== props ||
               (props = workInProgress.memoizedProps),
             (fn = props.children),
@@ -3649,8 +3546,7 @@ function ReactFiberBeginWork(
               workInProgress.stateNode.containerInfo
             ),
             (props = workInProgress.pendingProps),
-            didPerformWorkStackCursor.current ||
-            workInProgress.memoizedProps !== props
+            hasLegacyContextChanged() || workInProgress.memoizedProps !== props
               ? (null === current
                   ? (workInProgress.child = reconcileChildFibers(
                       workInProgress,
@@ -3681,7 +3577,7 @@ function ReactFiberBeginWork(
         case 10:
           return (
             (renderExpirationTime = workInProgress.pendingProps),
-            didPerformWorkStackCursor.current ||
+            hasLegacyContextChanged() ||
             workInProgress.memoizedProps !== renderExpirationTime
               ? (reconcileChildren(
                   current,
@@ -3699,7 +3595,7 @@ function ReactFiberBeginWork(
         case 11:
           return (
             (renderExpirationTime = workInProgress.pendingProps.children),
-            didPerformWorkStackCursor.current ||
+            hasLegacyContextChanged() ||
             (null !== renderExpirationTime &&
               workInProgress.memoizedProps !== renderExpirationTime)
               ? (reconcileChildren(
@@ -3729,7 +3625,7 @@ function ReactFiberBeginWork(
             props = fn._currentValue;
             var changedBits = fn._changedBits;
             if (
-              didPerformWorkStackCursor.current ||
+              hasLegacyContextChanged() ||
               0 !== changedBits ||
               updateQueue !== unmaskedContext
             ) {
@@ -3769,7 +3665,13 @@ function ReactFiberBeginWork(
     }
   };
 }
-function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
+function ReactFiberCompleteWork(
+  config,
+  hostContext,
+  legacyContext,
+  newContext,
+  hydrationContext
+) {
   function markUpdate(workInProgress) {
     workInProgress.effectTag |= 4;
   }
@@ -3802,6 +3704,9 @@ function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
     popHostContext = hostContext.popHostContext,
     getHostContext = hostContext.getHostContext,
     popHostContainer = hostContext.popHostContainer,
+    popLegacyContextProvider = legacyContext.popContextProvider,
+    popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject,
+    popProvider = newContext.popProvider,
     prepareToHydrateHostInstance =
       hydrationContext.prepareToHydrateHostInstance,
     prepareToHydrateHostTextInstance =
@@ -3901,7 +3806,7 @@ function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
           return null;
         case 2:
           return (
-            popContextProvider(workInProgress),
+            popLegacyContextProvider(workInProgress),
             (current = workInProgress.stateNode),
             (newProps = workInProgress.updateQueue),
             null !== newProps &&
@@ -3914,8 +3819,7 @@ function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
           );
         case 3:
           popHostContainer(workInProgress);
-          pop(didPerformWorkStackCursor, workInProgress);
-          pop(contextStackCursor, workInProgress);
+          popTopLevelLegacyContextObject(workInProgress);
           newProps = workInProgress.stateNode;
           newProps.pendingContext &&
             ((newProps.context = newProps.pendingContext),
@@ -4099,11 +4003,16 @@ function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
 }
 function ReactFiberUnwindWork(
   hostContext,
+  legacyContext,
+  newContext,
   scheduleWork,
   isAlreadyFailedLegacyErrorBoundary
 ) {
   var popHostContainer = hostContext.popHostContainer,
-    popHostContext = hostContext.popHostContext;
+    popHostContext = hostContext.popHostContext,
+    popLegacyContextProvider = legacyContext.popContextProvider,
+    popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject,
+    popProvider = newContext.popProvider;
   return {
     throwException: function(returnFiber, sourceFiber, rawValue) {
       sourceFiber.effectTag |= 512;
@@ -4144,7 +4053,7 @@ function ReactFiberUnwindWork(
     unwindWork: function(workInProgress) {
       switch (workInProgress.tag) {
         case 2:
-          popContextProvider(workInProgress);
+          popLegacyContextProvider(workInProgress);
           var effectTag = workInProgress.effectTag;
           return effectTag & 1024
             ? ((workInProgress.effectTag = (effectTag & -1025) | 64),
@@ -4153,8 +4062,7 @@ function ReactFiberUnwindWork(
         case 3:
           return (
             popHostContainer(workInProgress),
-            pop(didPerformWorkStackCursor, workInProgress),
-            pop(contextStackCursor, workInProgress),
+            popTopLevelLegacyContextObject(workInProgress),
             (effectTag = workInProgress.effectTag),
             effectTag & 1024
               ? ((workInProgress.effectTag = (effectTag & -1025) | 64),
@@ -4170,6 +4078,25 @@ function ReactFiberUnwindWork(
         default:
           return null;
       }
+    },
+    unwindInterruptedWork: function(interruptedWork) {
+      switch (interruptedWork.tag) {
+        case 2:
+          popLegacyContextProvider(interruptedWork);
+          break;
+        case 3:
+          popHostContainer(interruptedWork);
+          popTopLevelLegacyContextObject(interruptedWork);
+          break;
+        case 5:
+          popHostContext(interruptedWork);
+          break;
+        case 4:
+          popHostContainer(interruptedWork);
+          break;
+        case 13:
+          popProvider(interruptedWork);
+      }
     }
   };
 }
@@ -4425,7 +4352,7 @@ function ReactFiberCommitWork(
   invariant(!1, "Mutating reconciler is disabled.");
 }
 var NO_CONTEXT = {};
-function ReactFiberHostContext(config) {
+function ReactFiberHostContext(config, stack) {
   function requiredContext(c) {
     invariant(
       c !== NO_CONTEXT,
@@ -4434,10 +4361,13 @@ function ReactFiberHostContext(config) {
     return c;
   }
   var getChildHostContext = config.getChildHostContext,
-    getRootHostContext = config.getRootHostContext,
-    contextStackCursor = { current: NO_CONTEXT },
-    contextFiberStackCursor = { current: NO_CONTEXT },
-    rootInstanceStackCursor = { current: NO_CONTEXT };
+    getRootHostContext = config.getRootHostContext;
+  config = stack.createCursor;
+  var push = stack.push,
+    pop = stack.pop,
+    contextStackCursor = config(NO_CONTEXT),
+    contextFiberStackCursor = config(NO_CONTEXT),
+    rootInstanceStackCursor = config(NO_CONTEXT);
   return {
     getHostContext: function() {
       return requiredContext(contextStackCursor.current);
@@ -4467,10 +4397,6 @@ function ReactFiberHostContext(config) {
       context !== rootInstance &&
         (push(contextFiberStackCursor, fiber, fiber),
         push(contextStackCursor, rootInstance, fiber));
-    },
-    resetHostContainer: function() {
-      contextStackCursor.current = NO_CONTEXT;
-      rootInstanceStackCursor.current = NO_CONTEXT;
     }
   };
 }
@@ -4630,22 +4556,198 @@ function ReactFiberHydrationContext(config) {
     }
   };
 }
-function ReactFiberScheduler(config) {
-  function resetContextStack() {
-    for (; -1 < index; ) (valueStack[index] = null), index--;
+function ReactFiberLegacyContext(stack) {
+  function cacheContext(workInProgress, unmaskedContext, maskedContext) {
+    workInProgress = workInProgress.stateNode;
+    workInProgress.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext;
+    workInProgress.__reactInternalMemoizedMaskedChildContext = maskedContext;
+  }
+  function isContextProvider(fiber) {
+    return 2 === fiber.tag && null != fiber.type.childContextTypes;
+  }
+  function processChildContext(fiber, parentContext) {
+    var instance = fiber.stateNode,
+      childContextTypes = fiber.type.childContextTypes;
+    if ("function" !== typeof instance.getChildContext) return parentContext;
+    instance = instance.getChildContext();
+    for (var contextKey in instance)
+      invariant(
+        contextKey in childContextTypes,
+        '%s.getChildContext(): key "%s" is not defined in childContextTypes.',
+        getComponentName(fiber) || "Unknown",
+        contextKey
+      );
+    return Object.assign({}, parentContext, instance);
+  }
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop,
+    contextStackCursor = createCursor(emptyObject),
+    didPerformWorkStackCursor = createCursor(!1),
     previousContext = emptyObject;
-    contextStackCursor.current = emptyObject;
-    didPerformWorkStackCursor.current = !1;
-    resetHostContainer();
-    for (var i = index$1; -1 < i; i--) {
-      var context = stack[i].type.context;
-      context._currentValue = context._defaultValue;
-      context._changedBits = 0;
-      changedBitsStack[i] = null;
-      currentValueStack[i] = null;
-      stack[i] = null;
+  return {
+    getUnmaskedContext: function(workInProgress) {
+      return isContextProvider(workInProgress)
+        ? previousContext
+        : contextStackCursor.current;
+    },
+    cacheContext: cacheContext,
+    getMaskedContext: function(workInProgress, unmaskedContext) {
+      var contextTypes = workInProgress.type.contextTypes;
+      if (!contextTypes) return emptyObject;
+      var instance = workInProgress.stateNode;
+      if (
+        instance &&
+        instance.__reactInternalMemoizedUnmaskedChildContext === unmaskedContext
+      )
+        return instance.__reactInternalMemoizedMaskedChildContext;
+      var context = {},
+        key;
+      for (key in contextTypes) context[key] = unmaskedContext[key];
+      instance && cacheContext(workInProgress, unmaskedContext, context);
+      return context;
+    },
+    hasContextChanged: function() {
+      return didPerformWorkStackCursor.current;
+    },
+    isContextConsumer: function(fiber) {
+      return 2 === fiber.tag && null != fiber.type.contextTypes;
+    },
+    isContextProvider: isContextProvider,
+    popContextProvider: function(fiber) {
+      isContextProvider(fiber) &&
+        (pop(didPerformWorkStackCursor, fiber), pop(contextStackCursor, fiber));
+    },
+    popTopLevelContextObject: function(fiber) {
+      pop(didPerformWorkStackCursor, fiber);
+      pop(contextStackCursor, fiber);
+    },
+    pushTopLevelContextObject: function(fiber, context, didChange) {
+      invariant(
+        null == contextStackCursor.cursor,
+        "Unexpected context found on stack. This error is likely caused by a bug in React. Please file an issue."
+      );
+      push(contextStackCursor, context, fiber);
+      push(didPerformWorkStackCursor, didChange, fiber);
+    },
+    processChildContext: processChildContext,
+    pushContextProvider: function(workInProgress) {
+      if (!isContextProvider(workInProgress)) return !1;
+      var instance = workInProgress.stateNode;
+      instance =
+        (instance && instance.__reactInternalMemoizedMergedChildContext) ||
+        emptyObject;
+      previousContext = contextStackCursor.current;
+      push(contextStackCursor, instance, workInProgress);
+      push(
+        didPerformWorkStackCursor,
+        didPerformWorkStackCursor.current,
+        workInProgress
+      );
+      return !0;
+    },
+    invalidateContextProvider: function(workInProgress, didChange) {
+      var instance = workInProgress.stateNode;
+      invariant(
+        instance,
+        "Expected to have an instance by this point. This error is likely caused by a bug in React. Please file an issue."
+      );
+      if (didChange) {
+        var mergedContext = processChildContext(
+          workInProgress,
+          previousContext
+        );
+        instance.__reactInternalMemoizedMergedChildContext = mergedContext;
+        pop(didPerformWorkStackCursor, workInProgress);
+        pop(contextStackCursor, workInProgress);
+        push(contextStackCursor, mergedContext, workInProgress);
+      } else pop(didPerformWorkStackCursor, workInProgress);
+      push(didPerformWorkStackCursor, didChange, workInProgress);
+    },
+    findCurrentUnmaskedContext: function(fiber) {
+      for (
+        invariant(
+          2 === isFiberMountedImpl(fiber) && 2 === fiber.tag,
+          "Expected subtree parent to be a mounted class component. This error is likely caused by a bug in React. Please file an issue."
+        );
+        3 !== fiber.tag;
+
+      ) {
+        if (isContextProvider(fiber))
+          return fiber.stateNode.__reactInternalMemoizedMergedChildContext;
+        fiber = fiber["return"];
+        invariant(
+          fiber,
+          "Found unexpected detached subtree parent. This error is likely caused by a bug in React. Please file an issue."
+        );
+      }
+      return fiber.stateNode.context;
     }
-    index$1 = -1;
+  };
+}
+function ReactFiberNewContext(stack) {
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop,
+    providerCursor = createCursor(null),
+    valueCursor = createCursor(null),
+    changedBitsCursor = createCursor(0);
+  return {
+    pushProvider: function(providerFiber) {
+      var context = providerFiber.type.context;
+      push(changedBitsCursor, context._changedBits, providerFiber);
+      push(valueCursor, context._currentValue, providerFiber);
+      push(providerCursor, providerFiber, providerFiber);
+      context._currentValue = providerFiber.pendingProps.value;
+      context._changedBits = providerFiber.stateNode;
+    },
+    popProvider: function(providerFiber) {
+      var changedBits = changedBitsCursor.current,
+        currentValue = valueCursor.current;
+      pop(providerCursor, providerFiber);
+      pop(valueCursor, providerFiber);
+      pop(changedBitsCursor, providerFiber);
+      providerFiber = providerFiber.type.context;
+      providerFiber._currentValue = currentValue;
+      providerFiber._changedBits = changedBits;
+    }
+  };
+}
+function ReactFiberStack() {
+  var valueStack = [],
+    index = -1;
+  return {
+    createCursor: function(defaultValue) {
+      return { current: defaultValue };
+    },
+    isEmpty: function() {
+      return -1 === index;
+    },
+    pop: function(cursor) {
+      0 > index ||
+        ((cursor.current = valueStack[index]),
+        (valueStack[index] = null),
+        index--);
+    },
+    push: function(cursor, value) {
+      index++;
+      valueStack[index] = cursor.current;
+      cursor.current = value;
+    },
+    checkThatStackIsEmpty: function() {},
+    resetStackAfterFatalErrorInDev: function() {}
+  };
+}
+function ReactFiberScheduler(config) {
+  function resetStack() {
+    if (null !== nextUnitOfWork)
+      for (
+        var interruptedWork = nextUnitOfWork["return"];
+        null !== interruptedWork;
+
+      )
+        unwindInterruptedWork(interruptedWork),
+          (interruptedWork = interruptedWork["return"]);
     nextRoot = null;
     nextRenderExpirationTime = 0;
     nextUnitOfWork = null;
@@ -4751,7 +4853,7 @@ function ReactFiberScheduler(config) {
       root !== nextRoot ||
       null === nextUnitOfWork
     )
-      resetContextStack(),
+      resetStack(),
         (nextRoot = root),
         (nextRenderExpirationTime = expirationTime),
         (nextUnitOfWork = createWorkInProgress(
@@ -4881,7 +4983,7 @@ function ReactFiberScheduler(config) {
             !isWorking &&
               0 !== nextRenderExpirationTime &&
               expirationTime < nextRenderExpirationTime &&
-              resetContextStack();
+              resetStack();
             (nextRoot === root && isWorking) ||
               requestWork(root, expirationTime);
             nestedUpdateCount > NESTED_UPDATE_LIMIT &&
@@ -5225,25 +5327,37 @@ function ReactFiberScheduler(config) {
     nextFlushedRoot.remainingExpirationTime = 0;
     hasUnhandledError || ((hasUnhandledError = !0), (unhandledError = error));
   }
-  var hostContext = ReactFiberHostContext(config),
-    hydrationContext = ReactFiberHydrationContext(config),
-    resetHostContainer = hostContext.resetHostContainer,
+  var stack = ReactFiberStack(),
+    hostContext = ReactFiberHostContext(config, stack),
+    legacyContext = ReactFiberLegacyContext(stack);
+  stack = ReactFiberNewContext(stack);
+  var hydrationContext = ReactFiberHydrationContext(config),
     beginWork = ReactFiberBeginWork(
       config,
       hostContext,
+      legacyContext,
+      stack,
       hydrationContext,
       scheduleWork,
       computeExpirationForFiber
     ).beginWork,
-    completeWork = ReactFiberCompleteWork(config, hostContext, hydrationContext)
-      .completeWork;
+    completeWork = ReactFiberCompleteWork(
+      config,
+      hostContext,
+      legacyContext,
+      stack,
+      hydrationContext
+    ).completeWork;
   hostContext = ReactFiberUnwindWork(
     hostContext,
+    legacyContext,
+    stack,
     scheduleWork,
     isAlreadyFailedLegacyErrorBoundary
   );
   var throwException = hostContext.throwException,
-    unwindWork = hostContext.unwindWork;
+    unwindWork = hostContext.unwindWork,
+    unwindInterruptedWork = hostContext.unwindInterruptedWork;
   hostContext = ReactFiberCommitWork(
     config,
     onCommitPhaseError,
@@ -5402,7 +5516,8 @@ function ReactFiberScheduler(config) {
       result <= lastUniqueAsyncExpiration &&
         (result = lastUniqueAsyncExpiration + 1);
       return (lastUniqueAsyncExpiration = result);
-    }
+    },
+    legacyContext: legacyContext
   };
 }
 function ReactFiberReconciler$1(config) {
@@ -5417,27 +5532,7 @@ function ReactFiberReconciler$1(config) {
     currentTime = container.current;
     if (parentComponent) {
       parentComponent = parentComponent._reactInternalFiber;
-      var parentContext;
-      b: {
-        invariant(
-          2 === isFiberMountedImpl(parentComponent) &&
-            2 === parentComponent.tag,
-          "Expected subtree parent to be a mounted class component. This error is likely caused by a bug in React. Please file an issue."
-        );
-        for (parentContext = parentComponent; 3 !== parentContext.tag; ) {
-          if (isContextProvider(parentContext)) {
-            parentContext =
-              parentContext.stateNode.__reactInternalMemoizedMergedChildContext;
-            break b;
-          }
-          parentContext = parentContext["return"];
-          invariant(
-            parentContext,
-            "Found unexpected detached subtree parent. This error is likely caused by a bug in React. Please file an issue."
-          );
-        }
-        parentContext = parentContext.stateNode.context;
-      }
+      var parentContext = findCurrentUnmaskedContext(parentComponent);
       parentComponent = isContextProvider(parentComponent)
         ? processChildContext(parentComponent, parentContext)
         : parentContext;
@@ -5466,7 +5561,11 @@ function ReactFiberReconciler$1(config) {
   config = ReactFiberScheduler(config);
   var recalculateCurrentTime = config.recalculateCurrentTime,
     computeExpirationForFiber = config.computeExpirationForFiber,
-    scheduleWork = config.scheduleWork;
+    scheduleWork = config.scheduleWork,
+    legacyContext = config.legacyContext,
+    findCurrentUnmaskedContext = legacyContext.findCurrentUnmaskedContext,
+    isContextProvider = legacyContext.isContextProvider,
+    processChildContext = legacyContext.processChildContext;
   return {
     createContainer: function(containerInfo, isAsync, hydrate) {
       isAsync = new FiberNode(3, null, null, isAsync ? 3 : 0);
diff --git a/Libraries/Renderer/ReactNativeRenderer-dev.js b/Libraries/Renderer/ReactNativeRenderer-dev.js
index d54c9f31c..8ea8bcf85 100644
--- a/Libraries/Renderer/ReactNativeRenderer-dev.js
+++ b/Libraries/Renderer/ReactNativeRenderer-dev.js
@@ -26,9 +26,9 @@ var deepDiffer = require("deepDiffer");
 var flattenStyle = require("flattenStyle");
 var React = require("react");
 var emptyObject = require("fbjs/lib/emptyObject");
-var checkPropTypes = require("prop-types/checkPropTypes");
 var shallowEqual = require("fbjs/lib/shallowEqual");
 var ExceptionsManager = require("ExceptionsManager");
+var checkPropTypes = require("prop-types/checkPropTypes");
 var deepFreezeAndThrowOnMutationInDev = require("deepFreezeAndThrowOnMutationInDev");
 
 var invokeGuardedCallback = function(name, func, context, a, b, c, d, e, f) {
@@ -4389,879 +4389,6 @@ function findCurrentHostFiberWithNoPortals(parent) {
   return null;
 }
 
-var valueStack = [];
-
-var fiberStack = void 0;
-
-{
-  fiberStack = [];
-}
-
-var index = -1;
-
-function createCursor(defaultValue) {
-  return {
-    current: defaultValue
-  };
-}
-
-function pop(cursor, fiber) {
-  if (index < 0) {
-    {
-      warning(false, "Unexpected pop.");
-    }
-    return;
-  }
-
-  {
-    if (fiber !== fiberStack[index]) {
-      warning(false, "Unexpected Fiber popped.");
-    }
-  }
-
-  cursor.current = valueStack[index];
-
-  valueStack[index] = null;
-
-  {
-    fiberStack[index] = null;
-  }
-
-  index--;
-}
-
-function push(cursor, value, fiber) {
-  index++;
-
-  valueStack[index] = cursor.current;
-
-  {
-    fiberStack[index] = fiber;
-  }
-
-  cursor.current = value;
-}
-
-function reset() {
-  while (index > -1) {
-    valueStack[index] = null;
-
-    {
-      fiberStack[index] = null;
-    }
-
-    index--;
-  }
-}
-
-var describeComponentFrame = function(name, source, ownerName) {
-  return (
-    "\n    in " +
-    (name || "Unknown") +
-    (source
-      ? " (at " +
-        source.fileName.replace(/^.*[\\\/]/, "") +
-        ":" +
-        source.lineNumber +
-        ")"
-      : ownerName ? " (created by " + ownerName + ")" : "")
-  );
-};
-
-function describeFiber(fiber) {
-  switch (fiber.tag) {
-    case IndeterminateComponent:
-    case FunctionalComponent:
-    case ClassComponent:
-    case HostComponent:
-      var owner = fiber._debugOwner;
-      var source = fiber._debugSource;
-      var name = getComponentName(fiber);
-      var ownerName = null;
-      if (owner) {
-        ownerName = getComponentName(owner);
-      }
-      return describeComponentFrame(name, source, ownerName);
-    default:
-      return "";
-  }
-}
-
-// This function can only be called with a work-in-progress fiber and
-// only during begin or complete phase. Do not call it under any other
-// circumstances.
-function getStackAddendumByWorkInProgressFiber(workInProgress) {
-  var info = "";
-  var node = workInProgress;
-  do {
-    info += describeFiber(node);
-    // Otherwise this return pointer might point to the wrong tree:
-    node = node["return"];
-  } while (node);
-  return info;
-}
-
-function getCurrentFiberOwnerName() {
-  {
-    var fiber = ReactDebugCurrentFiber.current;
-    if (fiber === null) {
-      return null;
-    }
-    var owner = fiber._debugOwner;
-    if (owner !== null && typeof owner !== "undefined") {
-      return getComponentName(owner);
-    }
-  }
-  return null;
-}
-
-function getCurrentFiberStackAddendum() {
-  {
-    var fiber = ReactDebugCurrentFiber.current;
-    if (fiber === null) {
-      return null;
-    }
-    // Safe because if current fiber exists, we are reconciling,
-    // and it is guaranteed to be the work-in-progress version.
-    return getStackAddendumByWorkInProgressFiber(fiber);
-  }
-  return null;
-}
-
-function resetCurrentFiber() {
-  ReactDebugCurrentFrame.getCurrentStack = null;
-  ReactDebugCurrentFiber.current = null;
-  ReactDebugCurrentFiber.phase = null;
-}
-
-function setCurrentFiber(fiber) {
-  ReactDebugCurrentFrame.getCurrentStack = getCurrentFiberStackAddendum;
-  ReactDebugCurrentFiber.current = fiber;
-  ReactDebugCurrentFiber.phase = null;
-}
-
-function setCurrentPhase(phase) {
-  ReactDebugCurrentFiber.phase = phase;
-}
-
-var ReactDebugCurrentFiber = {
-  current: null,
-  phase: null,
-  resetCurrentFiber: resetCurrentFiber,
-  setCurrentFiber: setCurrentFiber,
-  setCurrentPhase: setCurrentPhase,
-  getCurrentFiberOwnerName: getCurrentFiberOwnerName,
-  getCurrentFiberStackAddendum: getCurrentFiberStackAddendum
-};
-
-// Re-export dynamic flags from the fbsource version.
-var _require = require("ReactFeatureFlags");
-
-var enableGetDerivedStateFromCatch = _require.enableGetDerivedStateFromCatch;
-var debugRenderPhaseSideEffects = _require.debugRenderPhaseSideEffects;
-var debugRenderPhaseSideEffectsForStrictMode =
-  _require.debugRenderPhaseSideEffectsForStrictMode;
-var warnAboutDeprecatedLifecycles = _require.warnAboutDeprecatedLifecycles;
-var replayFailedUnitOfWorkWithInvokeGuardedCallback =
-  _require.replayFailedUnitOfWorkWithInvokeGuardedCallback;
-
-var enableUserTimingAPI = true;
-var enableMutatingReconciler = true;
-var enableNoopReconciler = false;
-var enablePersistentReconciler = false;
-
-// Only used in www builds.
-
-// Prefix measurements so that it's possible to filter them.
-// Longer prefixes are hard to read in DevTools.
-var reactEmoji = "\u269B";
-var warningEmoji = "\u26D4";
-var supportsUserTiming =
-  typeof performance !== "undefined" &&
-  typeof performance.mark === "function" &&
-  typeof performance.clearMarks === "function" &&
-  typeof performance.measure === "function" &&
-  typeof performance.clearMeasures === "function";
-
-// Keep track of current fiber so that we know the path to unwind on pause.
-// TODO: this looks the same as nextUnitOfWork in scheduler. Can we unify them?
-var currentFiber = null;
-// If we're in the middle of user code, which fiber and method is it?
-// Reusing `currentFiber` would be confusing for this because user code fiber
-// can change during commit phase too, but we don't need to unwind it (since
-// lifecycles in the commit phase don't resemble a tree).
-var currentPhase = null;
-var currentPhaseFiber = null;
-// Did lifecycle hook schedule an update? This is often a performance problem,
-// so we will keep track of it, and include it in the report.
-// Track commits caused by cascading updates.
-var isCommitting = false;
-var hasScheduledUpdateInCurrentCommit = false;
-var hasScheduledUpdateInCurrentPhase = false;
-var commitCountInCurrentWorkLoop = 0;
-var effectCountInCurrentCommit = 0;
-var isWaitingForCallback = false;
-// During commits, we only show a measurement once per method name
-// to avoid stretch the commit phase with measurement overhead.
-var labelsInCurrentCommit = new Set();
-
-var formatMarkName = function(markName) {
-  return reactEmoji + " " + markName;
-};
-
-var formatLabel = function(label, warning$$1) {
-  var prefix = warning$$1 ? warningEmoji + " " : reactEmoji + " ";
-  var suffix = warning$$1 ? " Warning: " + warning$$1 : "";
-  return "" + prefix + label + suffix;
-};
-
-var beginMark = function(markName) {
-  performance.mark(formatMarkName(markName));
-};
-
-var clearMark = function(markName) {
-  performance.clearMarks(formatMarkName(markName));
-};
-
-var endMark = function(label, markName, warning$$1) {
-  var formattedMarkName = formatMarkName(markName);
-  var formattedLabel = formatLabel(label, warning$$1);
-  try {
-    performance.measure(formattedLabel, formattedMarkName);
-  } catch (err) {}
-  // If previous mark was missing for some reason, this will throw.
-  // This could only happen if React crashed in an unexpected place earlier.
-  // Don't pile on with more errors.
-
-  // Clear marks immediately to avoid growing buffer.
-  performance.clearMarks(formattedMarkName);
-  performance.clearMeasures(formattedLabel);
-};
-
-var getFiberMarkName = function(label, debugID) {
-  return label + " (#" + debugID + ")";
-};
-
-var getFiberLabel = function(componentName, isMounted, phase) {
-  if (phase === null) {
-    // These are composite component total time measurements.
-    return componentName + " [" + (isMounted ? "update" : "mount") + "]";
-  } else {
-    // Composite component methods.
-    return componentName + "." + phase;
-  }
-};
-
-var beginFiberMark = function(fiber, phase) {
-  var componentName = getComponentName(fiber) || "Unknown";
-  var debugID = fiber._debugID;
-  var isMounted = fiber.alternate !== null;
-  var label = getFiberLabel(componentName, isMounted, phase);
-
-  if (isCommitting && labelsInCurrentCommit.has(label)) {
-    // During the commit phase, we don't show duplicate labels because
-    // there is a fixed overhead for every measurement, and we don't
-    // want to stretch the commit phase beyond necessary.
-    return false;
-  }
-  labelsInCurrentCommit.add(label);
-
-  var markName = getFiberMarkName(label, debugID);
-  beginMark(markName);
-  return true;
-};
-
-var clearFiberMark = function(fiber, phase) {
-  var componentName = getComponentName(fiber) || "Unknown";
-  var debugID = fiber._debugID;
-  var isMounted = fiber.alternate !== null;
-  var label = getFiberLabel(componentName, isMounted, phase);
-  var markName = getFiberMarkName(label, debugID);
-  clearMark(markName);
-};
-
-var endFiberMark = function(fiber, phase, warning$$1) {
-  var componentName = getComponentName(fiber) || "Unknown";
-  var debugID = fiber._debugID;
-  var isMounted = fiber.alternate !== null;
-  var label = getFiberLabel(componentName, isMounted, phase);
-  var markName = getFiberMarkName(label, debugID);
-  endMark(label, markName, warning$$1);
-};
-
-var shouldIgnoreFiber = function(fiber) {
-  // Host components should be skipped in the timeline.
-  // We could check typeof fiber.type, but does this work with RN?
-  switch (fiber.tag) {
-    case HostRoot:
-    case HostComponent:
-    case HostText:
-    case HostPortal:
-    case CallComponent:
-    case ReturnComponent:
-    case Fragment:
-    case ContextProvider:
-    case ContextConsumer:
-      return true;
-    default:
-      return false;
-  }
-};
-
-var clearPendingPhaseMeasurement = function() {
-  if (currentPhase !== null && currentPhaseFiber !== null) {
-    clearFiberMark(currentPhaseFiber, currentPhase);
-  }
-  currentPhaseFiber = null;
-  currentPhase = null;
-  hasScheduledUpdateInCurrentPhase = false;
-};
-
-var pauseTimers = function() {
-  // Stops all currently active measurements so that they can be resumed
-  // if we continue in a later deferred loop from the same unit of work.
-  var fiber = currentFiber;
-  while (fiber) {
-    if (fiber._debugIsCurrentlyTiming) {
-      endFiberMark(fiber, null, null);
-    }
-    fiber = fiber["return"];
-  }
-};
-
-var resumeTimersRecursively = function(fiber) {
-  if (fiber["return"] !== null) {
-    resumeTimersRecursively(fiber["return"]);
-  }
-  if (fiber._debugIsCurrentlyTiming) {
-    beginFiberMark(fiber, null);
-  }
-};
-
-var resumeTimers = function() {
-  // Resumes all measurements that were active during the last deferred loop.
-  if (currentFiber !== null) {
-    resumeTimersRecursively(currentFiber);
-  }
-};
-
-function recordEffect() {
-  if (enableUserTimingAPI) {
-    effectCountInCurrentCommit++;
-  }
-}
-
-function recordScheduleUpdate() {
-  if (enableUserTimingAPI) {
-    if (isCommitting) {
-      hasScheduledUpdateInCurrentCommit = true;
-    }
-    if (
-      currentPhase !== null &&
-      currentPhase !== "componentWillMount" &&
-      currentPhase !== "componentWillReceiveProps"
-    ) {
-      hasScheduledUpdateInCurrentPhase = true;
-    }
-  }
-}
-
-function startRequestCallbackTimer() {
-  if (enableUserTimingAPI) {
-    if (supportsUserTiming && !isWaitingForCallback) {
-      isWaitingForCallback = true;
-      beginMark("(Waiting for async callback...)");
-    }
-  }
-}
-
-function stopRequestCallbackTimer(didExpire) {
-  if (enableUserTimingAPI) {
-    if (supportsUserTiming) {
-      isWaitingForCallback = false;
-      var warning$$1 = didExpire ? "React was blocked by main thread" : null;
-      endMark(
-        "(Waiting for async callback...)",
-        "(Waiting for async callback...)",
-        warning$$1
-      );
-    }
-  }
-}
-
-function startWorkTimer(fiber) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
-      return;
-    }
-    // If we pause, this is the fiber to unwind from.
-    currentFiber = fiber;
-    if (!beginFiberMark(fiber, null)) {
-      return;
-    }
-    fiber._debugIsCurrentlyTiming = true;
-  }
-}
-
-function cancelWorkTimer(fiber) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
-      return;
-    }
-    // Remember we shouldn't complete measurement for this fiber.
-    // Otherwise flamechart will be deep even for small updates.
-    fiber._debugIsCurrentlyTiming = false;
-    clearFiberMark(fiber, null);
-  }
-}
-
-function stopWorkTimer(fiber) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
-      return;
-    }
-    // If we pause, its parent is the fiber to unwind from.
-    currentFiber = fiber["return"];
-    if (!fiber._debugIsCurrentlyTiming) {
-      return;
-    }
-    fiber._debugIsCurrentlyTiming = false;
-    endFiberMark(fiber, null, null);
-  }
-}
-
-function stopFailedWorkTimer(fiber) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
-      return;
-    }
-    // If we pause, its parent is the fiber to unwind from.
-    currentFiber = fiber["return"];
-    if (!fiber._debugIsCurrentlyTiming) {
-      return;
-    }
-    fiber._debugIsCurrentlyTiming = false;
-    var warning$$1 = "An error was thrown inside this error boundary";
-    endFiberMark(fiber, null, warning$$1);
-  }
-}
-
-function startPhaseTimer(fiber, phase) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    clearPendingPhaseMeasurement();
-    if (!beginFiberMark(fiber, phase)) {
-      return;
-    }
-    currentPhaseFiber = fiber;
-    currentPhase = phase;
-  }
-}
-
-function stopPhaseTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    if (currentPhase !== null && currentPhaseFiber !== null) {
-      var warning$$1 = hasScheduledUpdateInCurrentPhase
-        ? "Scheduled a cascading update"
-        : null;
-      endFiberMark(currentPhaseFiber, currentPhase, warning$$1);
-    }
-    currentPhase = null;
-    currentPhaseFiber = null;
-  }
-}
-
-function startWorkLoopTimer(nextUnitOfWork) {
-  if (enableUserTimingAPI) {
-    currentFiber = nextUnitOfWork;
-    if (!supportsUserTiming) {
-      return;
-    }
-    commitCountInCurrentWorkLoop = 0;
-    // This is top level call.
-    // Any other measurements are performed within.
-    beginMark("(React Tree Reconciliation)");
-    // Resume any measurements that were in progress during the last loop.
-    resumeTimers();
-  }
-}
-
-function stopWorkLoopTimer(interruptedBy) {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    var warning$$1 = null;
-    if (interruptedBy !== null) {
-      if (interruptedBy.tag === HostRoot) {
-        warning$$1 = "A top-level update interrupted the previous render";
-      } else {
-        var componentName = getComponentName(interruptedBy) || "Unknown";
-        warning$$1 =
-          "An update to " + componentName + " interrupted the previous render";
-      }
-    } else if (commitCountInCurrentWorkLoop > 1) {
-      warning$$1 = "There were cascading updates";
-    }
-    commitCountInCurrentWorkLoop = 0;
-    // Pause any measurements until the next loop.
-    pauseTimers();
-    endMark(
-      "(React Tree Reconciliation)",
-      "(React Tree Reconciliation)",
-      warning$$1
-    );
-  }
-}
-
-function startCommitTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    isCommitting = true;
-    hasScheduledUpdateInCurrentCommit = false;
-    labelsInCurrentCommit.clear();
-    beginMark("(Committing Changes)");
-  }
-}
-
-function stopCommitTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-
-    var warning$$1 = null;
-    if (hasScheduledUpdateInCurrentCommit) {
-      warning$$1 = "Lifecycle hook scheduled a cascading update";
-    } else if (commitCountInCurrentWorkLoop > 0) {
-      warning$$1 = "Caused by a cascading update in earlier commit";
-    }
-    hasScheduledUpdateInCurrentCommit = false;
-    commitCountInCurrentWorkLoop++;
-    isCommitting = false;
-    labelsInCurrentCommit.clear();
-
-    endMark("(Committing Changes)", "(Committing Changes)", warning$$1);
-  }
-}
-
-function startCommitHostEffectsTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    effectCountInCurrentCommit = 0;
-    beginMark("(Committing Host Effects)");
-  }
-}
-
-function stopCommitHostEffectsTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    var count = effectCountInCurrentCommit;
-    effectCountInCurrentCommit = 0;
-    endMark(
-      "(Committing Host Effects: " + count + " Total)",
-      "(Committing Host Effects)",
-      null
-    );
-  }
-}
-
-function startCommitLifeCyclesTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    effectCountInCurrentCommit = 0;
-    beginMark("(Calling Lifecycle Methods)");
-  }
-}
-
-function stopCommitLifeCyclesTimer() {
-  if (enableUserTimingAPI) {
-    if (!supportsUserTiming) {
-      return;
-    }
-    var count = effectCountInCurrentCommit;
-    effectCountInCurrentCommit = 0;
-    endMark(
-      "(Calling Lifecycle Methods: " + count + " Total)",
-      "(Calling Lifecycle Methods)",
-      null
-    );
-  }
-}
-
-var warnedAboutMissingGetChildContext = void 0;
-
-{
-  warnedAboutMissingGetChildContext = {};
-}
-
-// A cursor to the current merged context object on the stack.
-var contextStackCursor = createCursor(emptyObject);
-// A cursor to a boolean indicating whether the context has changed.
-var didPerformWorkStackCursor = createCursor(false);
-// Keep track of the previous context object that was on the stack.
-// We use this to get access to the parent context after we have already
-// pushed the next context provider, and now need to merge their contexts.
-var previousContext = emptyObject;
-
-function getUnmaskedContext(workInProgress) {
-  var hasOwnContext = isContextProvider(workInProgress);
-  if (hasOwnContext) {
-    // If the fiber is a context provider itself, when we read its context
-    // we have already pushed its own child context on the stack. A context
-    // provider should not "see" its own child context. Therefore we read the
-    // previous (parent) context instead for a context provider.
-    return previousContext;
-  }
-  return contextStackCursor.current;
-}
-
-function cacheContext(workInProgress, unmaskedContext, maskedContext) {
-  var instance = workInProgress.stateNode;
-  instance.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext;
-  instance.__reactInternalMemoizedMaskedChildContext = maskedContext;
-}
-
-function getMaskedContext(workInProgress, unmaskedContext) {
-  var type = workInProgress.type;
-  var contextTypes = type.contextTypes;
-  if (!contextTypes) {
-    return emptyObject;
-  }
-
-  // Avoid recreating masked context unless unmasked context has changed.
-  // Failing to do this will result in unnecessary calls to componentWillReceiveProps.
-  // This may trigger infinite loops if componentWillReceiveProps calls setState.
-  var instance = workInProgress.stateNode;
-  if (
-    instance &&
-    instance.__reactInternalMemoizedUnmaskedChildContext === unmaskedContext
-  ) {
-    return instance.__reactInternalMemoizedMaskedChildContext;
-  }
-
-  var context = {};
-  for (var key in contextTypes) {
-    context[key] = unmaskedContext[key];
-  }
-
-  {
-    var name = getComponentName(workInProgress) || "Unknown";
-    checkPropTypes(
-      contextTypes,
-      context,
-      "context",
-      name,
-      ReactDebugCurrentFiber.getCurrentFiberStackAddendum
-    );
-  }
-
-  // Cache unmasked context so we can avoid recreating masked context unless necessary.
-  // Context is created before the class component is instantiated so check for instance.
-  if (instance) {
-    cacheContext(workInProgress, unmaskedContext, context);
-  }
-
-  return context;
-}
-
-function hasContextChanged() {
-  return didPerformWorkStackCursor.current;
-}
-
-function isContextConsumer(fiber) {
-  return fiber.tag === ClassComponent && fiber.type.contextTypes != null;
-}
-
-function isContextProvider(fiber) {
-  return fiber.tag === ClassComponent && fiber.type.childContextTypes != null;
-}
-
-function popContextProvider(fiber) {
-  if (!isContextProvider(fiber)) {
-    return;
-  }
-
-  pop(didPerformWorkStackCursor, fiber);
-  pop(contextStackCursor, fiber);
-}
-
-function popTopLevelContextObject(fiber) {
-  pop(didPerformWorkStackCursor, fiber);
-  pop(contextStackCursor, fiber);
-}
-
-function pushTopLevelContextObject(fiber, context, didChange) {
-  invariant(
-    contextStackCursor.cursor == null,
-    "Unexpected context found on stack. " +
-      "This error is likely caused by a bug in React. Please file an issue."
-  );
-
-  push(contextStackCursor, context, fiber);
-  push(didPerformWorkStackCursor, didChange, fiber);
-}
-
-function processChildContext(fiber, parentContext) {
-  var instance = fiber.stateNode;
-  var childContextTypes = fiber.type.childContextTypes;
-
-  // TODO (bvaughn) Replace this behavior with an invariant() in the future.
-  // It has only been added in Fiber to match the (unintentional) behavior in Stack.
-  if (typeof instance.getChildContext !== "function") {
-    {
-      var componentName = getComponentName(fiber) || "Unknown";
-
-      if (!warnedAboutMissingGetChildContext[componentName]) {
-        warnedAboutMissingGetChildContext[componentName] = true;
-        warning(
-          false,
-          "%s.childContextTypes is specified but there is no getChildContext() method " +
-            "on the instance. You can either define getChildContext() on %s or remove " +
-            "childContextTypes from it.",
-          componentName,
-          componentName
-        );
-      }
-    }
-    return parentContext;
-  }
-
-  var childContext = void 0;
-  {
-    ReactDebugCurrentFiber.setCurrentPhase("getChildContext");
-  }
-  startPhaseTimer(fiber, "getChildContext");
-  childContext = instance.getChildContext();
-  stopPhaseTimer();
-  {
-    ReactDebugCurrentFiber.setCurrentPhase(null);
-  }
-  for (var contextKey in childContext) {
-    invariant(
-      contextKey in childContextTypes,
-      '%s.getChildContext(): key "%s" is not defined in childContextTypes.',
-      getComponentName(fiber) || "Unknown",
-      contextKey
-    );
-  }
-  {
-    var name = getComponentName(fiber) || "Unknown";
-    checkPropTypes(
-      childContextTypes,
-      childContext,
-      "child context",
-      name,
-      // In practice, there is one case in which we won't get a stack. It's when
-      // somebody calls unstable_renderSubtreeIntoContainer() and we process
-      // context from the parent component instance. The stack will be missing
-      // because it's outside of the reconciliation, and so the pointer has not
-      // been set. This is rare and doesn't matter. We'll also remove that API.
-      ReactDebugCurrentFiber.getCurrentFiberStackAddendum
-    );
-  }
-
-  return Object.assign({}, parentContext, childContext);
-}
-
-function pushContextProvider(workInProgress) {
-  if (!isContextProvider(workInProgress)) {
-    return false;
-  }
-
-  var instance = workInProgress.stateNode;
-  // We push the context as early as possible to ensure stack integrity.
-  // If the instance does not exist yet, we will push null at first,
-  // and replace it on the stack later when invalidating the context.
-  var memoizedMergedChildContext =
-    (instance && instance.__reactInternalMemoizedMergedChildContext) ||
-    emptyObject;
-
-  // Remember the parent context so we can merge with it later.
-  // Inherit the parent's did-perform-work value to avoid inadvertently blocking updates.
-  previousContext = contextStackCursor.current;
-  push(contextStackCursor, memoizedMergedChildContext, workInProgress);
-  push(
-    didPerformWorkStackCursor,
-    didPerformWorkStackCursor.current,
-    workInProgress
-  );
-
-  return true;
-}
-
-function invalidateContextProvider(workInProgress, didChange) {
-  var instance = workInProgress.stateNode;
-  invariant(
-    instance,
-    "Expected to have an instance by this point. " +
-      "This error is likely caused by a bug in React. Please file an issue."
-  );
-
-  if (didChange) {
-    // Merge parent and own context.
-    // Skip this if we're not updating due to sCU.
-    // This avoids unnecessarily recomputing memoized values.
-    var mergedContext = processChildContext(workInProgress, previousContext);
-    instance.__reactInternalMemoizedMergedChildContext = mergedContext;
-
-    // Replace the old (or empty) context with the new one.
-    // It is important to unwind the context in the reverse order.
-    pop(didPerformWorkStackCursor, workInProgress);
-    pop(contextStackCursor, workInProgress);
-    // Now push the new context and mark that it has changed.
-    push(contextStackCursor, mergedContext, workInProgress);
-    push(didPerformWorkStackCursor, didChange, workInProgress);
-  } else {
-    pop(didPerformWorkStackCursor, workInProgress);
-    push(didPerformWorkStackCursor, didChange, workInProgress);
-  }
-}
-
-function resetContext() {
-  previousContext = emptyObject;
-  contextStackCursor.current = emptyObject;
-  didPerformWorkStackCursor.current = false;
-}
-
-function findCurrentUnmaskedContext(fiber) {
-  // Currently this is only used with renderSubtreeIntoContainer; not sure if it
-  // makes sense elsewhere
-  invariant(
-    isFiberMounted(fiber) && fiber.tag === ClassComponent,
-    "Expected subtree parent to be a mounted class component. " +
-      "This error is likely caused by a bug in React. Please file an issue."
-  );
-
-  var node = fiber;
-  while (node.tag !== HostRoot) {
-    if (isContextProvider(node)) {
-      return node.stateNode.__reactInternalMemoizedMergedChildContext;
-    }
-    var parent = node["return"];
-    invariant(
-      parent,
-      "Found unexpected detached subtree parent. " +
-        "This error is likely caused by a bug in React. Please file an issue."
-    );
-    node = parent;
-  }
-  return node.stateNode.context;
-}
-
 // Max 31 bit integer. The max integer size in V8 for 32-bit systems.
 // Math.pow(2, 30) - 1
 // 0b111111111111111111111111111111
@@ -5699,6 +4826,53 @@ function onCommitUnmount(fiber) {
   }
 }
 
+var describeComponentFrame = function(name, source, ownerName) {
+  return (
+    "\n    in " +
+    (name || "Unknown") +
+    (source
+      ? " (at " +
+        source.fileName.replace(/^.*[\\\/]/, "") +
+        ":" +
+        source.lineNumber +
+        ")"
+      : ownerName ? " (created by " + ownerName + ")" : "")
+  );
+};
+
+function describeFiber(fiber) {
+  switch (fiber.tag) {
+    case IndeterminateComponent:
+    case FunctionalComponent:
+    case ClassComponent:
+    case HostComponent:
+      var owner = fiber._debugOwner;
+      var source = fiber._debugSource;
+      var name = getComponentName(fiber);
+      var ownerName = null;
+      if (owner) {
+        ownerName = getComponentName(owner);
+      }
+      return describeComponentFrame(name, source, ownerName);
+    default:
+      return "";
+  }
+}
+
+// This function can only be called with a work-in-progress fiber and
+// only during begin or complete phase. Do not call it under any other
+// circumstances.
+function getStackAddendumByWorkInProgressFiber(workInProgress) {
+  var info = "";
+  var node = workInProgress;
+  do {
+    info += describeFiber(node);
+    // Otherwise this return pointer might point to the wrong tree:
+    node = node["return"];
+  } while (node);
+  return info;
+}
+
 /**
  * Forked from fbjs/warning:
  * https://github.com/facebook/fbjs/blob/e66ba20ad5be433eb54423f2b097d829324d9de6/packages/fbjs/src/__forks__/warning.js
@@ -6033,6 +5207,507 @@ var ReactStrictModeWarnings = {
   };
 }
 
+// Re-export dynamic flags from the fbsource version.
+var _require = require("ReactFeatureFlags");
+
+var enableGetDerivedStateFromCatch = _require.enableGetDerivedStateFromCatch;
+var debugRenderPhaseSideEffects = _require.debugRenderPhaseSideEffects;
+var debugRenderPhaseSideEffectsForStrictMode =
+  _require.debugRenderPhaseSideEffectsForStrictMode;
+var warnAboutDeprecatedLifecycles = _require.warnAboutDeprecatedLifecycles;
+var replayFailedUnitOfWorkWithInvokeGuardedCallback =
+  _require.replayFailedUnitOfWorkWithInvokeGuardedCallback;
+
+var enableUserTimingAPI = true;
+var enableMutatingReconciler = true;
+var enableNoopReconciler = false;
+var enablePersistentReconciler = false;
+
+// Only used in www builds.
+
+function getCurrentFiberOwnerName() {
+  {
+    var fiber = ReactDebugCurrentFiber.current;
+    if (fiber === null) {
+      return null;
+    }
+    var owner = fiber._debugOwner;
+    if (owner !== null && typeof owner !== "undefined") {
+      return getComponentName(owner);
+    }
+  }
+  return null;
+}
+
+function getCurrentFiberStackAddendum() {
+  {
+    var fiber = ReactDebugCurrentFiber.current;
+    if (fiber === null) {
+      return null;
+    }
+    // Safe because if current fiber exists, we are reconciling,
+    // and it is guaranteed to be the work-in-progress version.
+    return getStackAddendumByWorkInProgressFiber(fiber);
+  }
+  return null;
+}
+
+function resetCurrentFiber() {
+  ReactDebugCurrentFrame.getCurrentStack = null;
+  ReactDebugCurrentFiber.current = null;
+  ReactDebugCurrentFiber.phase = null;
+}
+
+function setCurrentFiber(fiber) {
+  ReactDebugCurrentFrame.getCurrentStack = getCurrentFiberStackAddendum;
+  ReactDebugCurrentFiber.current = fiber;
+  ReactDebugCurrentFiber.phase = null;
+}
+
+function setCurrentPhase(phase) {
+  ReactDebugCurrentFiber.phase = phase;
+}
+
+var ReactDebugCurrentFiber = {
+  current: null,
+  phase: null,
+  resetCurrentFiber: resetCurrentFiber,
+  setCurrentFiber: setCurrentFiber,
+  setCurrentPhase: setCurrentPhase,
+  getCurrentFiberOwnerName: getCurrentFiberOwnerName,
+  getCurrentFiberStackAddendum: getCurrentFiberStackAddendum
+};
+
+// Prefix measurements so that it's possible to filter them.
+// Longer prefixes are hard to read in DevTools.
+var reactEmoji = "\u269B";
+var warningEmoji = "\u26D4";
+var supportsUserTiming =
+  typeof performance !== "undefined" &&
+  typeof performance.mark === "function" &&
+  typeof performance.clearMarks === "function" &&
+  typeof performance.measure === "function" &&
+  typeof performance.clearMeasures === "function";
+
+// Keep track of current fiber so that we know the path to unwind on pause.
+// TODO: this looks the same as nextUnitOfWork in scheduler. Can we unify them?
+var currentFiber = null;
+// If we're in the middle of user code, which fiber and method is it?
+// Reusing `currentFiber` would be confusing for this because user code fiber
+// can change during commit phase too, but we don't need to unwind it (since
+// lifecycles in the commit phase don't resemble a tree).
+var currentPhase = null;
+var currentPhaseFiber = null;
+// Did lifecycle hook schedule an update? This is often a performance problem,
+// so we will keep track of it, and include it in the report.
+// Track commits caused by cascading updates.
+var isCommitting = false;
+var hasScheduledUpdateInCurrentCommit = false;
+var hasScheduledUpdateInCurrentPhase = false;
+var commitCountInCurrentWorkLoop = 0;
+var effectCountInCurrentCommit = 0;
+var isWaitingForCallback = false;
+// During commits, we only show a measurement once per method name
+// to avoid stretch the commit phase with measurement overhead.
+var labelsInCurrentCommit = new Set();
+
+var formatMarkName = function(markName) {
+  return reactEmoji + " " + markName;
+};
+
+var formatLabel = function(label, warning$$1) {
+  var prefix = warning$$1 ? warningEmoji + " " : reactEmoji + " ";
+  var suffix = warning$$1 ? " Warning: " + warning$$1 : "";
+  return "" + prefix + label + suffix;
+};
+
+var beginMark = function(markName) {
+  performance.mark(formatMarkName(markName));
+};
+
+var clearMark = function(markName) {
+  performance.clearMarks(formatMarkName(markName));
+};
+
+var endMark = function(label, markName, warning$$1) {
+  var formattedMarkName = formatMarkName(markName);
+  var formattedLabel = formatLabel(label, warning$$1);
+  try {
+    performance.measure(formattedLabel, formattedMarkName);
+  } catch (err) {}
+  // If previous mark was missing for some reason, this will throw.
+  // This could only happen if React crashed in an unexpected place earlier.
+  // Don't pile on with more errors.
+
+  // Clear marks immediately to avoid growing buffer.
+  performance.clearMarks(formattedMarkName);
+  performance.clearMeasures(formattedLabel);
+};
+
+var getFiberMarkName = function(label, debugID) {
+  return label + " (#" + debugID + ")";
+};
+
+var getFiberLabel = function(componentName, isMounted, phase) {
+  if (phase === null) {
+    // These are composite component total time measurements.
+    return componentName + " [" + (isMounted ? "update" : "mount") + "]";
+  } else {
+    // Composite component methods.
+    return componentName + "." + phase;
+  }
+};
+
+var beginFiberMark = function(fiber, phase) {
+  var componentName = getComponentName(fiber) || "Unknown";
+  var debugID = fiber._debugID;
+  var isMounted = fiber.alternate !== null;
+  var label = getFiberLabel(componentName, isMounted, phase);
+
+  if (isCommitting && labelsInCurrentCommit.has(label)) {
+    // During the commit phase, we don't show duplicate labels because
+    // there is a fixed overhead for every measurement, and we don't
+    // want to stretch the commit phase beyond necessary.
+    return false;
+  }
+  labelsInCurrentCommit.add(label);
+
+  var markName = getFiberMarkName(label, debugID);
+  beginMark(markName);
+  return true;
+};
+
+var clearFiberMark = function(fiber, phase) {
+  var componentName = getComponentName(fiber) || "Unknown";
+  var debugID = fiber._debugID;
+  var isMounted = fiber.alternate !== null;
+  var label = getFiberLabel(componentName, isMounted, phase);
+  var markName = getFiberMarkName(label, debugID);
+  clearMark(markName);
+};
+
+var endFiberMark = function(fiber, phase, warning$$1) {
+  var componentName = getComponentName(fiber) || "Unknown";
+  var debugID = fiber._debugID;
+  var isMounted = fiber.alternate !== null;
+  var label = getFiberLabel(componentName, isMounted, phase);
+  var markName = getFiberMarkName(label, debugID);
+  endMark(label, markName, warning$$1);
+};
+
+var shouldIgnoreFiber = function(fiber) {
+  // Host components should be skipped in the timeline.
+  // We could check typeof fiber.type, but does this work with RN?
+  switch (fiber.tag) {
+    case HostRoot:
+    case HostComponent:
+    case HostText:
+    case HostPortal:
+    case CallComponent:
+    case ReturnComponent:
+    case Fragment:
+    case ContextProvider:
+    case ContextConsumer:
+      return true;
+    default:
+      return false;
+  }
+};
+
+var clearPendingPhaseMeasurement = function() {
+  if (currentPhase !== null && currentPhaseFiber !== null) {
+    clearFiberMark(currentPhaseFiber, currentPhase);
+  }
+  currentPhaseFiber = null;
+  currentPhase = null;
+  hasScheduledUpdateInCurrentPhase = false;
+};
+
+var pauseTimers = function() {
+  // Stops all currently active measurements so that they can be resumed
+  // if we continue in a later deferred loop from the same unit of work.
+  var fiber = currentFiber;
+  while (fiber) {
+    if (fiber._debugIsCurrentlyTiming) {
+      endFiberMark(fiber, null, null);
+    }
+    fiber = fiber["return"];
+  }
+};
+
+var resumeTimersRecursively = function(fiber) {
+  if (fiber["return"] !== null) {
+    resumeTimersRecursively(fiber["return"]);
+  }
+  if (fiber._debugIsCurrentlyTiming) {
+    beginFiberMark(fiber, null);
+  }
+};
+
+var resumeTimers = function() {
+  // Resumes all measurements that were active during the last deferred loop.
+  if (currentFiber !== null) {
+    resumeTimersRecursively(currentFiber);
+  }
+};
+
+function recordEffect() {
+  if (enableUserTimingAPI) {
+    effectCountInCurrentCommit++;
+  }
+}
+
+function recordScheduleUpdate() {
+  if (enableUserTimingAPI) {
+    if (isCommitting) {
+      hasScheduledUpdateInCurrentCommit = true;
+    }
+    if (
+      currentPhase !== null &&
+      currentPhase !== "componentWillMount" &&
+      currentPhase !== "componentWillReceiveProps"
+    ) {
+      hasScheduledUpdateInCurrentPhase = true;
+    }
+  }
+}
+
+function startRequestCallbackTimer() {
+  if (enableUserTimingAPI) {
+    if (supportsUserTiming && !isWaitingForCallback) {
+      isWaitingForCallback = true;
+      beginMark("(Waiting for async callback...)");
+    }
+  }
+}
+
+function stopRequestCallbackTimer(didExpire) {
+  if (enableUserTimingAPI) {
+    if (supportsUserTiming) {
+      isWaitingForCallback = false;
+      var warning$$1 = didExpire ? "React was blocked by main thread" : null;
+      endMark(
+        "(Waiting for async callback...)",
+        "(Waiting for async callback...)",
+        warning$$1
+      );
+    }
+  }
+}
+
+function startWorkTimer(fiber) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
+      return;
+    }
+    // If we pause, this is the fiber to unwind from.
+    currentFiber = fiber;
+    if (!beginFiberMark(fiber, null)) {
+      return;
+    }
+    fiber._debugIsCurrentlyTiming = true;
+  }
+}
+
+function cancelWorkTimer(fiber) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
+      return;
+    }
+    // Remember we shouldn't complete measurement for this fiber.
+    // Otherwise flamechart will be deep even for small updates.
+    fiber._debugIsCurrentlyTiming = false;
+    clearFiberMark(fiber, null);
+  }
+}
+
+function stopWorkTimer(fiber) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
+      return;
+    }
+    // If we pause, its parent is the fiber to unwind from.
+    currentFiber = fiber["return"];
+    if (!fiber._debugIsCurrentlyTiming) {
+      return;
+    }
+    fiber._debugIsCurrentlyTiming = false;
+    endFiberMark(fiber, null, null);
+  }
+}
+
+function stopFailedWorkTimer(fiber) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming || shouldIgnoreFiber(fiber)) {
+      return;
+    }
+    // If we pause, its parent is the fiber to unwind from.
+    currentFiber = fiber["return"];
+    if (!fiber._debugIsCurrentlyTiming) {
+      return;
+    }
+    fiber._debugIsCurrentlyTiming = false;
+    var warning$$1 = "An error was thrown inside this error boundary";
+    endFiberMark(fiber, null, warning$$1);
+  }
+}
+
+function startPhaseTimer(fiber, phase) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    clearPendingPhaseMeasurement();
+    if (!beginFiberMark(fiber, phase)) {
+      return;
+    }
+    currentPhaseFiber = fiber;
+    currentPhase = phase;
+  }
+}
+
+function stopPhaseTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    if (currentPhase !== null && currentPhaseFiber !== null) {
+      var warning$$1 = hasScheduledUpdateInCurrentPhase
+        ? "Scheduled a cascading update"
+        : null;
+      endFiberMark(currentPhaseFiber, currentPhase, warning$$1);
+    }
+    currentPhase = null;
+    currentPhaseFiber = null;
+  }
+}
+
+function startWorkLoopTimer(nextUnitOfWork) {
+  if (enableUserTimingAPI) {
+    currentFiber = nextUnitOfWork;
+    if (!supportsUserTiming) {
+      return;
+    }
+    commitCountInCurrentWorkLoop = 0;
+    // This is top level call.
+    // Any other measurements are performed within.
+    beginMark("(React Tree Reconciliation)");
+    // Resume any measurements that were in progress during the last loop.
+    resumeTimers();
+  }
+}
+
+function stopWorkLoopTimer(interruptedBy) {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    var warning$$1 = null;
+    if (interruptedBy !== null) {
+      if (interruptedBy.tag === HostRoot) {
+        warning$$1 = "A top-level update interrupted the previous render";
+      } else {
+        var componentName = getComponentName(interruptedBy) || "Unknown";
+        warning$$1 =
+          "An update to " + componentName + " interrupted the previous render";
+      }
+    } else if (commitCountInCurrentWorkLoop > 1) {
+      warning$$1 = "There were cascading updates";
+    }
+    commitCountInCurrentWorkLoop = 0;
+    // Pause any measurements until the next loop.
+    pauseTimers();
+    endMark(
+      "(React Tree Reconciliation)",
+      "(React Tree Reconciliation)",
+      warning$$1
+    );
+  }
+}
+
+function startCommitTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    isCommitting = true;
+    hasScheduledUpdateInCurrentCommit = false;
+    labelsInCurrentCommit.clear();
+    beginMark("(Committing Changes)");
+  }
+}
+
+function stopCommitTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+
+    var warning$$1 = null;
+    if (hasScheduledUpdateInCurrentCommit) {
+      warning$$1 = "Lifecycle hook scheduled a cascading update";
+    } else if (commitCountInCurrentWorkLoop > 0) {
+      warning$$1 = "Caused by a cascading update in earlier commit";
+    }
+    hasScheduledUpdateInCurrentCommit = false;
+    commitCountInCurrentWorkLoop++;
+    isCommitting = false;
+    labelsInCurrentCommit.clear();
+
+    endMark("(Committing Changes)", "(Committing Changes)", warning$$1);
+  }
+}
+
+function startCommitHostEffectsTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    effectCountInCurrentCommit = 0;
+    beginMark("(Committing Host Effects)");
+  }
+}
+
+function stopCommitHostEffectsTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    var count = effectCountInCurrentCommit;
+    effectCountInCurrentCommit = 0;
+    endMark(
+      "(Committing Host Effects: " + count + " Total)",
+      "(Committing Host Effects)",
+      null
+    );
+  }
+}
+
+function startCommitLifeCyclesTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    effectCountInCurrentCommit = 0;
+    beginMark("(Calling Lifecycle Methods)");
+  }
+}
+
+function stopCommitLifeCyclesTimer() {
+  if (enableUserTimingAPI) {
+    if (!supportsUserTiming) {
+      return;
+    }
+    var count = effectCountInCurrentCommit;
+    effectCountInCurrentCommit = 0;
+    endMark(
+      "(Calling Lifecycle Methods: " + count + " Total)",
+      "(Calling Lifecycle Methods)",
+      null
+    );
+  }
+}
+
 var didWarnUpdateInsideUpdate = void 0;
 
 {
@@ -6430,12 +6105,20 @@ function callGetDerivedStateFromCatch(ctor, capturedValues) {
 }
 
 var ReactFiberClassComponent = function(
+  legacyContext,
   scheduleWork,
   computeExpirationForFiber,
   memoizeProps,
   memoizeState
 ) {
+  var cacheContext = legacyContext.cacheContext,
+    getMaskedContext = legacyContext.getMaskedContext,
+    getUnmaskedContext = legacyContext.getUnmaskedContext,
+    isContextConsumer = legacyContext.isContextConsumer,
+    hasContextChanged = legacyContext.hasContextChanged;
+
   // Class component state updater
+
   var updater = {
     isMounted: isMounted,
     enqueueSetState: function(instance, partialState, callback) {
@@ -8583,71 +8266,6 @@ function cloneChildFibers(current, workInProgress) {
   newChild.sibling = null;
 }
 
-var changedBitsStack = [];
-var currentValueStack = [];
-var stack = [];
-var index$1 = -1;
-
-var rendererSigil = void 0;
-{
-  // Use this to detect multiple renderers using the same context
-  rendererSigil = {};
-}
-
-function pushProvider(providerFiber) {
-  var context = providerFiber.type.context;
-  index$1 += 1;
-  changedBitsStack[index$1] = context._changedBits;
-  currentValueStack[index$1] = context._currentValue;
-  stack[index$1] = providerFiber;
-  context._currentValue = providerFiber.pendingProps.value;
-  context._changedBits = providerFiber.stateNode;
-
-  {
-    warning(
-      context._currentRenderer === null ||
-        context._currentRenderer === rendererSigil,
-      "Detected multiple renderers concurrently rendering the " +
-        "same context provider. This is currently unsupported."
-    );
-    context._currentRenderer = rendererSigil;
-  }
-}
-
-function popProvider(providerFiber) {
-  {
-    warning(
-      index$1 > -1 && providerFiber === stack[index$1],
-      "Unexpected pop."
-    );
-  }
-  var changedBits = changedBitsStack[index$1];
-  var currentValue = currentValueStack[index$1];
-  changedBitsStack[index$1] = null;
-  currentValueStack[index$1] = null;
-  stack[index$1] = null;
-  index$1 -= 1;
-  var context = providerFiber.type.context;
-  context._currentValue = currentValue;
-  context._changedBits = changedBits;
-}
-
-function resetProviderStack() {
-  for (var i = index$1; i > -1; i--) {
-    var providerFiber = stack[i];
-    var context = providerFiber.type.context;
-    context._currentValue = context._defaultValue;
-    context._changedBits = 0;
-    changedBitsStack[i] = null;
-    currentValueStack[i] = null;
-    stack[i] = null;
-    {
-      context._currentRenderer = null;
-    }
-  }
-  index$1 = -1;
-}
-
 var didWarnAboutBadClass = void 0;
 var didWarnAboutGetDerivedStateOnFunctionalComponent = void 0;
 var didWarnAboutStatelessRefs = void 0;
@@ -8661,6 +8279,8 @@ var didWarnAboutStatelessRefs = void 0;
 var ReactFiberBeginWork = function(
   config,
   hostContext,
+  legacyContext,
+  newContext,
   hydrationContext,
   scheduleWork,
   computeExpirationForFiber
@@ -8669,12 +8289,20 @@ var ReactFiberBeginWork = function(
     shouldDeprioritizeSubtree = config.shouldDeprioritizeSubtree;
   var pushHostContext = hostContext.pushHostContext,
     pushHostContainer = hostContext.pushHostContainer;
+  var pushProvider = newContext.pushProvider;
+  var getMaskedContext = legacyContext.getMaskedContext,
+    getUnmaskedContext = legacyContext.getUnmaskedContext,
+    hasLegacyContextChanged = legacyContext.hasContextChanged,
+    pushLegacyContextProvider = legacyContext.pushContextProvider,
+    pushTopLevelContextObject = legacyContext.pushTopLevelContextObject,
+    invalidateContextProvider = legacyContext.invalidateContextProvider;
   var enterHydrationState = hydrationContext.enterHydrationState,
     resetHydrationState = hydrationContext.resetHydrationState,
     tryToClaimNextHydratableInstance =
       hydrationContext.tryToClaimNextHydratableInstance;
 
   var _ReactFiberClassCompo = ReactFiberClassComponent(
+      legacyContext,
       scheduleWork,
       computeExpirationForFiber,
       memoizeProps,
@@ -8742,7 +8370,7 @@ var ReactFiberBeginWork = function(
 
   function updateFragment(current, workInProgress) {
     var nextChildren = workInProgress.pendingProps;
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (workInProgress.memoizedProps === nextChildren) {
@@ -8755,7 +8383,7 @@ var ReactFiberBeginWork = function(
 
   function updateMode(current, workInProgress) {
     var nextChildren = workInProgress.pendingProps.children;
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (
@@ -8784,7 +8412,7 @@ var ReactFiberBeginWork = function(
     var fn = workInProgress.type;
     var nextProps = workInProgress.pendingProps;
 
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else {
@@ -8817,7 +8445,7 @@ var ReactFiberBeginWork = function(
     // Push context providers early to prevent context stack mismatches.
     // During mounting we don't know the child context yet as the instance doesn't exist.
     // We will invalidate the child context in finishClassComponent() right after rendering.
-    var hasContext = pushContextProvider(workInProgress);
+    var hasContext = pushLegacyContextProvider(workInProgress);
     var shouldUpdate = void 0;
     if (current === null) {
       if (workInProgress.stateNode === null) {
@@ -9042,7 +8670,7 @@ var ReactFiberBeginWork = function(
     var nextProps = workInProgress.pendingProps;
     var prevProps = current !== null ? current.memoizedProps : null;
 
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (memoizedProps === nextProps) {
@@ -9177,7 +8805,7 @@ var ReactFiberBeginWork = function(
       // Push context providers early to prevent context stack mismatches.
       // During mounting we don't know the child context yet as the instance doesn't exist.
       // We will invalidate the child context in finishClassComponent() right after rendering.
-      var hasContext = pushContextProvider(workInProgress);
+      var hasContext = pushLegacyContextProvider(workInProgress);
       adoptClassInstance(workInProgress, value);
       mountClassInstance(workInProgress, renderExpirationTime);
       return finishClassComponent(
@@ -9250,7 +8878,7 @@ var ReactFiberBeginWork = function(
 
   function updateCallComponent(current, workInProgress, renderExpirationTime) {
     var nextProps = workInProgress.pendingProps;
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (workInProgress.memoizedProps === nextProps) {
@@ -9293,7 +8921,7 @@ var ReactFiberBeginWork = function(
   ) {
     pushHostContainer(workInProgress, workInProgress.stateNode.containerInfo);
     var nextChildren = workInProgress.pendingProps;
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (workInProgress.memoizedProps === nextChildren) {
@@ -9327,6 +8955,10 @@ var ReactFiberBeginWork = function(
     renderExpirationTime
   ) {
     var fiber = workInProgress.child;
+    if (fiber !== null) {
+      // Set the return pointer of the child to the work-in-progress fiber.
+      fiber["return"] = workInProgress;
+    }
     while (fiber !== null) {
       var nextFiber = void 0;
       // Visit this fiber.
@@ -9419,7 +9051,7 @@ var ReactFiberBeginWork = function(
     var newProps = workInProgress.pendingProps;
     var oldProps = workInProgress.memoizedProps;
 
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (oldProps === newProps) {
@@ -9515,7 +9147,7 @@ var ReactFiberBeginWork = function(
     var newValue = context._currentValue;
     var changedBits = context._changedBits;
 
-    if (hasContextChanged()) {
+    if (hasLegacyContextChanged()) {
       // Normally we can bail out on props equality but if context has changed
       // we don't do the bailout and we have to reuse existing props instead.
     } else if (changedBits === 0 && oldProps === newProps) {
@@ -9612,7 +9244,7 @@ var ReactFiberBeginWork = function(
         pushHostRootContext(workInProgress);
         break;
       case ClassComponent:
-        pushContextProvider(workInProgress);
+        pushLegacyContextProvider(workInProgress);
         break;
       case HostPortal:
         pushHostContainer(
@@ -9725,7 +9357,13 @@ var ReactFiberBeginWork = function(
   };
 };
 
-var ReactFiberCompleteWork = function(config, hostContext, hydrationContext) {
+var ReactFiberCompleteWork = function(
+  config,
+  hostContext,
+  legacyContext,
+  newContext,
+  hydrationContext
+) {
   var createInstance = config.createInstance,
     createTextInstance = config.createTextInstance,
     appendInitialChild = config.appendInitialChild,
@@ -9737,6 +9375,9 @@ var ReactFiberCompleteWork = function(config, hostContext, hydrationContext) {
     popHostContext = hostContext.popHostContext,
     getHostContext = hostContext.getHostContext,
     popHostContainer = hostContext.popHostContainer;
+  var popLegacyContextProvider = legacyContext.popContextProvider,
+    popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject;
+  var popProvider = newContext.popProvider;
   var prepareToHydrateHostInstance =
       hydrationContext.prepareToHydrateHostInstance,
     prepareToHydrateHostTextInstance =
@@ -10052,7 +9693,7 @@ var ReactFiberCompleteWork = function(config, hostContext, hydrationContext) {
         return null;
       case ClassComponent: {
         // We are leaving this subtree, so pop context if any.
-        popContextProvider(workInProgress);
+        popLegacyContextProvider(workInProgress);
 
         // If this component caught an error, schedule an error log effect.
         var instance = workInProgress.stateNode;
@@ -10071,7 +9712,7 @@ var ReactFiberCompleteWork = function(config, hostContext, hydrationContext) {
       }
       case HostRoot: {
         popHostContainer(workInProgress);
-        popTopLevelContextObject(workInProgress);
+        popTopLevelLegacyContextObject(workInProgress);
         var fiberRoot = workInProgress.stateNode;
         if (fiberRoot.pendingContext) {
           fiberRoot.context = fiberRoot.pendingContext;
@@ -10298,11 +9939,16 @@ function createCapturedValue(value, source) {
 
 var ReactFiberUnwindWork = function(
   hostContext,
+  legacyContext,
+  newContext,
   scheduleWork,
   isAlreadyFailedLegacyErrorBoundary
 ) {
   var popHostContainer = hostContext.popHostContainer,
     popHostContext = hostContext.popHostContext;
+  var popLegacyContextProvider = legacyContext.popContextProvider,
+    popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject;
+  var popProvider = newContext.popProvider;
 
   function throwException(returnFiber, sourceFiber, rawValue) {
     // The source fiber did not complete.
@@ -10358,7 +10004,7 @@ var ReactFiberUnwindWork = function(
   function unwindWork(workInProgress) {
     switch (workInProgress.tag) {
       case ClassComponent: {
-        popContextProvider(workInProgress);
+        popLegacyContextProvider(workInProgress);
         var effectTag = workInProgress.effectTag;
         if (effectTag & ShouldCapture) {
           workInProgress.effectTag = (effectTag & ~ShouldCapture) | DidCapture;
@@ -10368,7 +10014,7 @@ var ReactFiberUnwindWork = function(
       }
       case HostRoot: {
         popHostContainer(workInProgress);
-        popTopLevelContextObject(workInProgress);
+        popTopLevelLegacyContextObject(workInProgress);
         var _effectTag = workInProgress.effectTag;
         if (_effectTag & ShouldCapture) {
           workInProgress.effectTag = (_effectTag & ~ShouldCapture) | DidCapture;
@@ -10390,9 +10036,37 @@ var ReactFiberUnwindWork = function(
         return null;
     }
   }
+
+  function unwindInterruptedWork(interruptedWork) {
+    switch (interruptedWork.tag) {
+      case ClassComponent: {
+        popLegacyContextProvider(interruptedWork);
+        break;
+      }
+      case HostRoot: {
+        popHostContainer(interruptedWork);
+        popTopLevelLegacyContextObject(interruptedWork);
+        break;
+      }
+      case HostComponent: {
+        popHostContext(interruptedWork);
+        break;
+      }
+      case HostPortal:
+        popHostContainer(interruptedWork);
+        break;
+      case ContextProvider:
+        popProvider(interruptedWork);
+        break;
+      default:
+        break;
+    }
+  }
+
   return {
     throwException: throwException,
-    unwindWork: unwindWork
+    unwindWork: unwindWork,
+    unwindInterruptedWork: unwindInterruptedWork
   };
 };
 
@@ -10758,7 +10432,7 @@ var ReactFiberCommitWork = function(
             warning(
               false,
               "Unexpected ref object provided for %s. " +
-                "Use either a ref-setter function or Reacte.createRef().%s",
+                "Use either a ref-setter function or React.createRef().%s",
               getComponentName(finishedWork),
               getStackAddendumByWorkInProgressFiber(finishedWork)
             );
@@ -11264,9 +10938,12 @@ var ReactFiberCommitWork = function(
 
 var NO_CONTEXT = {};
 
-var ReactFiberHostContext = function(config) {
+var ReactFiberHostContext = function(config, stack) {
   var getChildHostContext = config.getChildHostContext,
     getRootHostContext = config.getRootHostContext;
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop;
 
   var contextStackCursor = createCursor(NO_CONTEXT);
   var contextFiberStackCursor = createCursor(NO_CONTEXT);
@@ -11337,19 +11014,13 @@ var ReactFiberHostContext = function(config) {
     pop(contextFiberStackCursor, fiber);
   }
 
-  function resetHostContainer() {
-    contextStackCursor.current = NO_CONTEXT;
-    rootInstanceStackCursor.current = NO_CONTEXT;
-  }
-
   return {
     getHostContext: getHostContext,
     getRootHostContainer: getRootHostContainer,
     popHostContainer: popHostContainer,
     popHostContext: popHostContext,
     pushHostContainer: pushHostContainer,
-    pushHostContext: pushHostContext,
-    resetHostContainer: resetHostContainer
+    pushHostContext: pushHostContext
   };
 };
 
@@ -11719,6 +11390,425 @@ var ReactFiberInstrumentation = {
 
 var ReactFiberInstrumentation_1 = ReactFiberInstrumentation;
 
+var warnedAboutMissingGetChildContext = void 0;
+
+{
+  warnedAboutMissingGetChildContext = {};
+}
+
+var ReactFiberLegacyContext = function(stack) {
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop;
+
+  // A cursor to the current merged context object on the stack.
+
+  var contextStackCursor = createCursor(emptyObject);
+  // A cursor to a boolean indicating whether the context has changed.
+  var didPerformWorkStackCursor = createCursor(false);
+  // Keep track of the previous context object that was on the stack.
+  // We use this to get access to the parent context after we have already
+  // pushed the next context provider, and now need to merge their contexts.
+  var previousContext = emptyObject;
+
+  function getUnmaskedContext(workInProgress) {
+    var hasOwnContext = isContextProvider(workInProgress);
+    if (hasOwnContext) {
+      // If the fiber is a context provider itself, when we read its context
+      // we have already pushed its own child context on the stack. A context
+      // provider should not "see" its own child context. Therefore we read the
+      // previous (parent) context instead for a context provider.
+      return previousContext;
+    }
+    return contextStackCursor.current;
+  }
+
+  function cacheContext(workInProgress, unmaskedContext, maskedContext) {
+    var instance = workInProgress.stateNode;
+    instance.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext;
+    instance.__reactInternalMemoizedMaskedChildContext = maskedContext;
+  }
+
+  function getMaskedContext(workInProgress, unmaskedContext) {
+    var type = workInProgress.type;
+    var contextTypes = type.contextTypes;
+    if (!contextTypes) {
+      return emptyObject;
+    }
+
+    // Avoid recreating masked context unless unmasked context has changed.
+    // Failing to do this will result in unnecessary calls to componentWillReceiveProps.
+    // This may trigger infinite loops if componentWillReceiveProps calls setState.
+    var instance = workInProgress.stateNode;
+    if (
+      instance &&
+      instance.__reactInternalMemoizedUnmaskedChildContext === unmaskedContext
+    ) {
+      return instance.__reactInternalMemoizedMaskedChildContext;
+    }
+
+    var context = {};
+    for (var key in contextTypes) {
+      context[key] = unmaskedContext[key];
+    }
+
+    {
+      var name = getComponentName(workInProgress) || "Unknown";
+      checkPropTypes(
+        contextTypes,
+        context,
+        "context",
+        name,
+        ReactDebugCurrentFiber.getCurrentFiberStackAddendum
+      );
+    }
+
+    // Cache unmasked context so we can avoid recreating masked context unless necessary.
+    // Context is created before the class component is instantiated so check for instance.
+    if (instance) {
+      cacheContext(workInProgress, unmaskedContext, context);
+    }
+
+    return context;
+  }
+
+  function hasContextChanged() {
+    return didPerformWorkStackCursor.current;
+  }
+
+  function isContextConsumer(fiber) {
+    return fiber.tag === ClassComponent && fiber.type.contextTypes != null;
+  }
+
+  function isContextProvider(fiber) {
+    return fiber.tag === ClassComponent && fiber.type.childContextTypes != null;
+  }
+
+  function popContextProvider(fiber) {
+    if (!isContextProvider(fiber)) {
+      return;
+    }
+
+    pop(didPerformWorkStackCursor, fiber);
+    pop(contextStackCursor, fiber);
+  }
+
+  function popTopLevelContextObject(fiber) {
+    pop(didPerformWorkStackCursor, fiber);
+    pop(contextStackCursor, fiber);
+  }
+
+  function pushTopLevelContextObject(fiber, context, didChange) {
+    invariant(
+      contextStackCursor.cursor == null,
+      "Unexpected context found on stack. " +
+        "This error is likely caused by a bug in React. Please file an issue."
+    );
+
+    push(contextStackCursor, context, fiber);
+    push(didPerformWorkStackCursor, didChange, fiber);
+  }
+
+  function processChildContext(fiber, parentContext) {
+    var instance = fiber.stateNode;
+    var childContextTypes = fiber.type.childContextTypes;
+
+    // TODO (bvaughn) Replace this behavior with an invariant() in the future.
+    // It has only been added in Fiber to match the (unintentional) behavior in Stack.
+    if (typeof instance.getChildContext !== "function") {
+      {
+        var componentName = getComponentName(fiber) || "Unknown";
+
+        if (!warnedAboutMissingGetChildContext[componentName]) {
+          warnedAboutMissingGetChildContext[componentName] = true;
+          warning(
+            false,
+            "%s.childContextTypes is specified but there is no getChildContext() method " +
+              "on the instance. You can either define getChildContext() on %s or remove " +
+              "childContextTypes from it.",
+            componentName,
+            componentName
+          );
+        }
+      }
+      return parentContext;
+    }
+
+    var childContext = void 0;
+    {
+      ReactDebugCurrentFiber.setCurrentPhase("getChildContext");
+    }
+    startPhaseTimer(fiber, "getChildContext");
+    childContext = instance.getChildContext();
+    stopPhaseTimer();
+    {
+      ReactDebugCurrentFiber.setCurrentPhase(null);
+    }
+    for (var contextKey in childContext) {
+      invariant(
+        contextKey in childContextTypes,
+        '%s.getChildContext(): key "%s" is not defined in childContextTypes.',
+        getComponentName(fiber) || "Unknown",
+        contextKey
+      );
+    }
+    {
+      var name = getComponentName(fiber) || "Unknown";
+      checkPropTypes(
+        childContextTypes,
+        childContext,
+        "child context",
+        name,
+        // In practice, there is one case in which we won't get a stack. It's when
+        // somebody calls unstable_renderSubtreeIntoContainer() and we process
+        // context from the parent component instance. The stack will be missing
+        // because it's outside of the reconciliation, and so the pointer has not
+        // been set. This is rare and doesn't matter. We'll also remove that API.
+        ReactDebugCurrentFiber.getCurrentFiberStackAddendum
+      );
+    }
+
+    return Object.assign({}, parentContext, childContext);
+  }
+
+  function pushContextProvider(workInProgress) {
+    if (!isContextProvider(workInProgress)) {
+      return false;
+    }
+
+    var instance = workInProgress.stateNode;
+    // We push the context as early as possible to ensure stack integrity.
+    // If the instance does not exist yet, we will push null at first,
+    // and replace it on the stack later when invalidating the context.
+    var memoizedMergedChildContext =
+      (instance && instance.__reactInternalMemoizedMergedChildContext) ||
+      emptyObject;
+
+    // Remember the parent context so we can merge with it later.
+    // Inherit the parent's did-perform-work value to avoid inadvertently blocking updates.
+    previousContext = contextStackCursor.current;
+    push(contextStackCursor, memoizedMergedChildContext, workInProgress);
+    push(
+      didPerformWorkStackCursor,
+      didPerformWorkStackCursor.current,
+      workInProgress
+    );
+
+    return true;
+  }
+
+  function invalidateContextProvider(workInProgress, didChange) {
+    var instance = workInProgress.stateNode;
+    invariant(
+      instance,
+      "Expected to have an instance by this point. " +
+        "This error is likely caused by a bug in React. Please file an issue."
+    );
+
+    if (didChange) {
+      // Merge parent and own context.
+      // Skip this if we're not updating due to sCU.
+      // This avoids unnecessarily recomputing memoized values.
+      var mergedContext = processChildContext(workInProgress, previousContext);
+      instance.__reactInternalMemoizedMergedChildContext = mergedContext;
+
+      // Replace the old (or empty) context with the new one.
+      // It is important to unwind the context in the reverse order.
+      pop(didPerformWorkStackCursor, workInProgress);
+      pop(contextStackCursor, workInProgress);
+      // Now push the new context and mark that it has changed.
+      push(contextStackCursor, mergedContext, workInProgress);
+      push(didPerformWorkStackCursor, didChange, workInProgress);
+    } else {
+      pop(didPerformWorkStackCursor, workInProgress);
+      push(didPerformWorkStackCursor, didChange, workInProgress);
+    }
+  }
+
+  function findCurrentUnmaskedContext(fiber) {
+    // Currently this is only used with renderSubtreeIntoContainer; not sure if it
+    // makes sense elsewhere
+    invariant(
+      isFiberMounted(fiber) && fiber.tag === ClassComponent,
+      "Expected subtree parent to be a mounted class component. " +
+        "This error is likely caused by a bug in React. Please file an issue."
+    );
+
+    var node = fiber;
+    while (node.tag !== HostRoot) {
+      if (isContextProvider(node)) {
+        return node.stateNode.__reactInternalMemoizedMergedChildContext;
+      }
+      var parent = node["return"];
+      invariant(
+        parent,
+        "Found unexpected detached subtree parent. " +
+          "This error is likely caused by a bug in React. Please file an issue."
+      );
+      node = parent;
+    }
+    return node.stateNode.context;
+  }
+
+  return {
+    getUnmaskedContext: getUnmaskedContext,
+    cacheContext: cacheContext,
+    getMaskedContext: getMaskedContext,
+    hasContextChanged: hasContextChanged,
+    isContextConsumer: isContextConsumer,
+    isContextProvider: isContextProvider,
+    popContextProvider: popContextProvider,
+    popTopLevelContextObject: popTopLevelContextObject,
+    pushTopLevelContextObject: pushTopLevelContextObject,
+    processChildContext: processChildContext,
+    pushContextProvider: pushContextProvider,
+    invalidateContextProvider: invalidateContextProvider,
+    findCurrentUnmaskedContext: findCurrentUnmaskedContext
+  };
+};
+
+var ReactFiberNewContext = function(stack) {
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop;
+
+  var providerCursor = createCursor(null);
+  var valueCursor = createCursor(null);
+  var changedBitsCursor = createCursor(0);
+
+  var rendererSigil = void 0;
+  {
+    // Use this to detect multiple renderers using the same context
+    rendererSigil = {};
+  }
+
+  function pushProvider(providerFiber) {
+    var context = providerFiber.type.context;
+
+    push(changedBitsCursor, context._changedBits, providerFiber);
+    push(valueCursor, context._currentValue, providerFiber);
+    push(providerCursor, providerFiber, providerFiber);
+
+    context._currentValue = providerFiber.pendingProps.value;
+    context._changedBits = providerFiber.stateNode;
+
+    {
+      warning(
+        context._currentRenderer === null ||
+          context._currentRenderer === rendererSigil,
+        "Detected multiple renderers concurrently rendering the " +
+          "same context provider. This is currently unsupported."
+      );
+      context._currentRenderer = rendererSigil;
+    }
+  }
+
+  function popProvider(providerFiber) {
+    var changedBits = changedBitsCursor.current;
+    var currentValue = valueCursor.current;
+
+    pop(providerCursor, providerFiber);
+    pop(valueCursor, providerFiber);
+    pop(changedBitsCursor, providerFiber);
+
+    var context = providerFiber.type.context;
+    context._currentValue = currentValue;
+    context._changedBits = changedBits;
+  }
+
+  return {
+    pushProvider: pushProvider,
+    popProvider: popProvider
+  };
+};
+
+var ReactFiberStack = function() {
+  var valueStack = [];
+
+  var fiberStack = void 0;
+
+  {
+    fiberStack = [];
+  }
+
+  var index = -1;
+
+  function createCursor(defaultValue) {
+    return {
+      current: defaultValue
+    };
+  }
+
+  function isEmpty() {
+    return index === -1;
+  }
+
+  function pop(cursor, fiber) {
+    if (index < 0) {
+      {
+        warning(false, "Unexpected pop.");
+      }
+      return;
+    }
+
+    {
+      if (fiber !== fiberStack[index]) {
+        warning(false, "Unexpected Fiber popped.");
+      }
+    }
+
+    cursor.current = valueStack[index];
+
+    valueStack[index] = null;
+
+    {
+      fiberStack[index] = null;
+    }
+
+    index--;
+  }
+
+  function push(cursor, value, fiber) {
+    index++;
+
+    valueStack[index] = cursor.current;
+
+    {
+      fiberStack[index] = fiber;
+    }
+
+    cursor.current = value;
+  }
+
+  function checkThatStackIsEmpty() {
+    {
+      if (index !== -1) {
+        warning(
+          false,
+          "Expected an empty stack. Something was not reset properly."
+        );
+      }
+    }
+  }
+
+  function resetStackAfterFatalErrorInDev() {
+    {
+      index = -1;
+      valueStack.length = 0;
+      fiberStack.length = 0;
+    }
+  }
+
+  return {
+    createCursor: createCursor,
+    isEmpty: isEmpty,
+    pop: pop,
+    push: push,
+    checkThatStackIsEmpty: checkThatStackIsEmpty,
+    resetStackAfterFatalErrorInDev: resetStackAfterFatalErrorInDev
+  };
+};
+
 var invokeGuardedCallback$2 = ReactErrorUtils.invokeGuardedCallback;
 var hasCaughtError = ReactErrorUtils.hasCaughtError;
 var clearCaughtError = ReactErrorUtils.clearCaughtError;
@@ -11779,16 +11869,23 @@ var warnAboutInvalidUpdates = void 0;
 }
 
 var ReactFiberScheduler = function(config) {
-  var hostContext = ReactFiberHostContext(config);
+  var stack = ReactFiberStack();
+  var hostContext = ReactFiberHostContext(config, stack);
+  var legacyContext = ReactFiberLegacyContext(stack);
+  var newContext = ReactFiberNewContext(stack);
   var popHostContext = hostContext.popHostContext,
     popHostContainer = hostContext.popHostContainer;
+  var popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject,
+    popLegacyContextProvider = legacyContext.popContextProvider;
+  var popProvider = newContext.popProvider;
 
   var hydrationContext = ReactFiberHydrationContext(config);
-  var resetHostContainer = hostContext.resetHostContainer;
 
   var _ReactFiberBeginWork = ReactFiberBeginWork(
       config,
       hostContext,
+      legacyContext,
+      newContext,
       hydrationContext,
       scheduleWork,
       computeExpirationForFiber
@@ -11798,17 +11895,22 @@ var ReactFiberScheduler = function(config) {
   var _ReactFiberCompleteWo = ReactFiberCompleteWork(
       config,
       hostContext,
+      legacyContext,
+      newContext,
       hydrationContext
     ),
     completeWork = _ReactFiberCompleteWo.completeWork;
 
   var _ReactFiberUnwindWork = ReactFiberUnwindWork(
       hostContext,
+      legacyContext,
+      newContext,
       scheduleWork,
       isAlreadyFailedLegacyErrorBoundary
     ),
     throwException = _ReactFiberUnwindWork.throwException,
-    unwindWork = _ReactFiberUnwindWork.unwindWork;
+    unwindWork = _ReactFiberUnwindWork.unwindWork,
+    unwindInterruptedWork = _ReactFiberUnwindWork.unwindInterruptedWork;
 
   var _ReactFiberCommitWork = ReactFiberCommitWork(
       config,
@@ -11877,13 +11979,13 @@ var ReactFiberScheduler = function(config) {
       switch (failedUnitOfWork.tag) {
         case HostRoot:
           popHostContainer(failedUnitOfWork);
-          popTopLevelContextObject(failedUnitOfWork);
+          popTopLevelLegacyContextObject(failedUnitOfWork);
           break;
         case HostComponent:
           popHostContext(failedUnitOfWork);
           break;
         case ClassComponent:
-          popContextProvider(failedUnitOfWork);
+          popLegacyContextProvider(failedUnitOfWork);
           break;
         case HostPortal:
           popHostContainer(failedUnitOfWork);
@@ -11903,18 +12005,18 @@ var ReactFiberScheduler = function(config) {
     };
   }
 
-  function resetContextStack() {
-    // Reset the stack
-    reset();
-    // Reset the cursors
-    resetContext();
-    resetHostContainer();
-
-    // TODO: Unify new context implementation with other stacks
-    resetProviderStack();
+  function resetStack() {
+    if (nextUnitOfWork !== null) {
+      var interruptedWork = nextUnitOfWork["return"];
+      while (interruptedWork !== null) {
+        unwindInterruptedWork(interruptedWork);
+        interruptedWork = interruptedWork["return"];
+      }
+    }
 
     {
       ReactStrictModeWarnings.discardPendingWarnings();
+      stack.checkThatStackIsEmpty();
     }
 
     nextRoot = null;
@@ -12438,7 +12540,7 @@ var ReactFiberScheduler = function(config) {
       nextUnitOfWork === null
     ) {
       // Reset the stack and start working from the root.
-      resetContextStack();
+      resetStack();
       nextRoot = root;
       nextRenderExpirationTime = expirationTime;
       nextUnitOfWork = createWorkInProgress(
@@ -12491,6 +12593,9 @@ var ReactFiberScheduler = function(config) {
     // Yield back to main thread.
     if (didFatal) {
       // There was a fatal error.
+      {
+        stack.resetStackAfterFatalErrorInDev();
+      }
       return null;
     } else if (nextUnitOfWork === null) {
       // We reached the root.
@@ -12691,7 +12796,7 @@ var ReactFiberScheduler = function(config) {
           ) {
             // This is an interruption. (Used for performance tracking.)
             interruptedBy = fiber;
-            resetContextStack();
+            resetStack();
           }
           if (nextRoot !== root || !isWorking) {
             requestWork(root, expirationTime);
@@ -13262,7 +13367,8 @@ var ReactFiberScheduler = function(config) {
     syncUpdates: syncUpdates,
     interactiveUpdates: interactiveUpdates,
     flushInteractiveUpdates: flushInteractiveUpdates,
-    computeUniqueAsyncExpiration: computeUniqueAsyncExpiration
+    computeUniqueAsyncExpiration: computeUniqueAsyncExpiration,
+    legacyContext: legacyContext
   };
 };
 
@@ -13275,18 +13381,6 @@ var didWarnAboutNestedUpdates = void 0;
 // 0 is PROD, 1 is DEV.
 // Might add PROFILE later.
 
-function getContextForSubtree(parentComponent) {
-  if (!parentComponent) {
-    return emptyObject;
-  }
-
-  var fiber = get(parentComponent);
-  var parentContext = findCurrentUnmaskedContext(fiber);
-  return isContextProvider(fiber)
-    ? processChildContext(fiber, parentContext)
-    : parentContext;
-}
-
 var ReactFiberReconciler$1 = function(config) {
   var getPublicInstance = config.getPublicInstance;
 
@@ -13305,7 +13399,24 @@ var ReactFiberReconciler$1 = function(config) {
     deferredUpdates = _ReactFiberScheduler.deferredUpdates,
     syncUpdates = _ReactFiberScheduler.syncUpdates,
     interactiveUpdates = _ReactFiberScheduler.interactiveUpdates,
-    flushInteractiveUpdates = _ReactFiberScheduler.flushInteractiveUpdates;
+    flushInteractiveUpdates = _ReactFiberScheduler.flushInteractiveUpdates,
+    legacyContext = _ReactFiberScheduler.legacyContext;
+
+  var findCurrentUnmaskedContext = legacyContext.findCurrentUnmaskedContext,
+    isContextProvider = legacyContext.isContextProvider,
+    processChildContext = legacyContext.processChildContext;
+
+  function getContextForSubtree(parentComponent) {
+    if (!parentComponent) {
+      return emptyObject;
+    }
+
+    var fiber = get(parentComponent);
+    var parentContext = findCurrentUnmaskedContext(fiber);
+    return isContextProvider(fiber)
+      ? processChildContext(fiber, parentContext)
+      : parentContext;
+  }
 
   function scheduleRootUpdate(
     current,
diff --git a/Libraries/Renderer/ReactNativeRenderer-prod.js b/Libraries/Renderer/ReactNativeRenderer-prod.js
index 258608b7f..f11aa6c82 100644
--- a/Libraries/Renderer/ReactNativeRenderer-prod.js
+++ b/Libraries/Renderer/ReactNativeRenderer-prod.js
@@ -1822,141 +1822,6 @@ function findCurrentHostFiberWithNoPortals(parent) {
   }
   return null;
 }
-var valueStack = [],
-  index = -1;
-function pop(cursor) {
-  0 > index ||
-    ((cursor.current = valueStack[index]), (valueStack[index] = null), index--);
-}
-function push(cursor, value) {
-  index++;
-  valueStack[index] = cursor.current;
-  cursor.current = value;
-}
-function getStackAddendumByWorkInProgressFiber(workInProgress) {
-  var info = "";
-  do {
-    a: switch (workInProgress.tag) {
-      case 0:
-      case 1:
-      case 2:
-      case 5:
-        var owner = workInProgress._debugOwner,
-          source = workInProgress._debugSource;
-        var JSCompiler_inline_result = getComponentName(workInProgress);
-        var ownerName = null;
-        owner && (ownerName = getComponentName(owner));
-        owner = source;
-        JSCompiler_inline_result =
-          "\n    in " +
-          (JSCompiler_inline_result || "Unknown") +
-          (owner
-            ? " (at " +
-              owner.fileName.replace(/^.*[\\\/]/, "") +
-              ":" +
-              owner.lineNumber +
-              ")"
-            : ownerName ? " (created by " + ownerName + ")" : "");
-        break a;
-      default:
-        JSCompiler_inline_result = "";
-    }
-    info += JSCompiler_inline_result;
-    workInProgress = workInProgress["return"];
-  } while (workInProgress);
-  return info;
-}
-var _require = require("ReactFeatureFlags"),
-  enableGetDerivedStateFromCatch = _require.enableGetDerivedStateFromCatch,
-  debugRenderPhaseSideEffects = _require.debugRenderPhaseSideEffects,
-  debugRenderPhaseSideEffectsForStrictMode =
-    _require.debugRenderPhaseSideEffectsForStrictMode;
-new Set();
-var contextStackCursor = { current: emptyObject },
-  didPerformWorkStackCursor = { current: !1 },
-  previousContext = emptyObject;
-function getUnmaskedContext(workInProgress) {
-  return isContextProvider(workInProgress)
-    ? previousContext
-    : contextStackCursor.current;
-}
-function getMaskedContext(workInProgress, unmaskedContext) {
-  var contextTypes = workInProgress.type.contextTypes;
-  if (!contextTypes) return emptyObject;
-  var instance = workInProgress.stateNode;
-  if (
-    instance &&
-    instance.__reactInternalMemoizedUnmaskedChildContext === unmaskedContext
-  )
-    return instance.__reactInternalMemoizedMaskedChildContext;
-  var context = {},
-    key;
-  for (key in contextTypes) context[key] = unmaskedContext[key];
-  instance &&
-    ((workInProgress = workInProgress.stateNode),
-    (workInProgress.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext),
-    (workInProgress.__reactInternalMemoizedMaskedChildContext = context));
-  return context;
-}
-function isContextProvider(fiber) {
-  return 2 === fiber.tag && null != fiber.type.childContextTypes;
-}
-function popContextProvider(fiber) {
-  isContextProvider(fiber) &&
-    (pop(didPerformWorkStackCursor, fiber), pop(contextStackCursor, fiber));
-}
-function pushTopLevelContextObject(fiber, context, didChange) {
-  invariant(
-    null == contextStackCursor.cursor,
-    "Unexpected context found on stack. This error is likely caused by a bug in React. Please file an issue."
-  );
-  push(contextStackCursor, context, fiber);
-  push(didPerformWorkStackCursor, didChange, fiber);
-}
-function processChildContext(fiber, parentContext) {
-  var instance = fiber.stateNode,
-    childContextTypes = fiber.type.childContextTypes;
-  if ("function" !== typeof instance.getChildContext) return parentContext;
-  instance = instance.getChildContext();
-  for (var contextKey in instance)
-    invariant(
-      contextKey in childContextTypes,
-      '%s.getChildContext(): key "%s" is not defined in childContextTypes.',
-      getComponentName(fiber) || "Unknown",
-      contextKey
-    );
-  return Object.assign({}, parentContext, instance);
-}
-function pushContextProvider(workInProgress) {
-  if (!isContextProvider(workInProgress)) return !1;
-  var instance = workInProgress.stateNode;
-  instance =
-    (instance && instance.__reactInternalMemoizedMergedChildContext) ||
-    emptyObject;
-  previousContext = contextStackCursor.current;
-  push(contextStackCursor, instance, workInProgress);
-  push(
-    didPerformWorkStackCursor,
-    didPerformWorkStackCursor.current,
-    workInProgress
-  );
-  return !0;
-}
-function invalidateContextProvider(workInProgress, didChange) {
-  var instance = workInProgress.stateNode;
-  invariant(
-    instance,
-    "Expected to have an instance by this point. This error is likely caused by a bug in React. Please file an issue."
-  );
-  if (didChange) {
-    var mergedContext = processChildContext(workInProgress, previousContext);
-    instance.__reactInternalMemoizedMergedChildContext = mergedContext;
-    pop(didPerformWorkStackCursor, workInProgress);
-    pop(contextStackCursor, workInProgress);
-    push(contextStackCursor, mergedContext, workInProgress);
-  } else pop(didPerformWorkStackCursor, workInProgress);
-  push(didPerformWorkStackCursor, didChange, workInProgress);
-}
 function FiberNode(tag, pendingProps, key, mode) {
   this.tag = tag;
   this.key = key;
@@ -2123,6 +1988,45 @@ function onCommitRoot(root) {
 function onCommitUnmount(fiber) {
   "function" === typeof onCommitFiberUnmount && onCommitFiberUnmount(fiber);
 }
+function getStackAddendumByWorkInProgressFiber(workInProgress) {
+  var info = "";
+  do {
+    a: switch (workInProgress.tag) {
+      case 0:
+      case 1:
+      case 2:
+      case 5:
+        var owner = workInProgress._debugOwner,
+          source = workInProgress._debugSource;
+        var JSCompiler_inline_result = getComponentName(workInProgress);
+        var ownerName = null;
+        owner && (ownerName = getComponentName(owner));
+        owner = source;
+        JSCompiler_inline_result =
+          "\n    in " +
+          (JSCompiler_inline_result || "Unknown") +
+          (owner
+            ? " (at " +
+              owner.fileName.replace(/^.*[\\\/]/, "") +
+              ":" +
+              owner.lineNumber +
+              ")"
+            : ownerName ? " (created by " + ownerName + ")" : "");
+        break a;
+      default:
+        JSCompiler_inline_result = "";
+    }
+    info += JSCompiler_inline_result;
+    workInProgress = workInProgress["return"];
+  } while (workInProgress);
+  return info;
+}
+var _require = require("ReactFeatureFlags"),
+  enableGetDerivedStateFromCatch = _require.enableGetDerivedStateFromCatch,
+  debugRenderPhaseSideEffects = _require.debugRenderPhaseSideEffects,
+  debugRenderPhaseSideEffectsForStrictMode =
+    _require.debugRenderPhaseSideEffectsForStrictMode;
+new Set();
 function createUpdateQueue(baseState) {
   return {
     baseState: baseState,
@@ -2294,6 +2198,7 @@ function callGetDerivedStateFromCatch(ctor, capturedValues) {
   return resultState;
 }
 function ReactFiberClassComponent(
+  legacyContext,
   scheduleWork,
   computeExpirationForFiber,
   memoizeProps,
@@ -2360,62 +2265,66 @@ function ReactFiberClassComponent(
         )
       );
   }
-  var updater = {
-    isMounted: isMounted,
-    enqueueSetState: function(instance, partialState, callback) {
-      instance = instance._reactInternalFiber;
-      callback = void 0 === callback ? null : callback;
-      var expirationTime = computeExpirationForFiber(instance);
-      insertUpdateIntoFiber(instance, {
-        expirationTime: expirationTime,
-        partialState: partialState,
-        callback: callback,
-        isReplace: !1,
-        isForced: !1,
-        capturedValue: null,
-        next: null
-      });
-      scheduleWork(instance, expirationTime);
-    },
-    enqueueReplaceState: function(instance, state, callback) {
-      instance = instance._reactInternalFiber;
-      callback = void 0 === callback ? null : callback;
-      var expirationTime = computeExpirationForFiber(instance);
-      insertUpdateIntoFiber(instance, {
-        expirationTime: expirationTime,
-        partialState: state,
-        callback: callback,
-        isReplace: !0,
-        isForced: !1,
-        capturedValue: null,
-        next: null
-      });
-      scheduleWork(instance, expirationTime);
-    },
-    enqueueForceUpdate: function(instance, callback) {
-      instance = instance._reactInternalFiber;
-      callback = void 0 === callback ? null : callback;
-      var expirationTime = computeExpirationForFiber(instance);
-      insertUpdateIntoFiber(instance, {
-        expirationTime: expirationTime,
-        partialState: null,
-        callback: callback,
-        isReplace: !1,
-        isForced: !0,
-        capturedValue: null,
-        next: null
-      });
-      scheduleWork(instance, expirationTime);
-    }
-  };
+  var cacheContext = legacyContext.cacheContext,
+    getMaskedContext = legacyContext.getMaskedContext,
+    getUnmaskedContext = legacyContext.getUnmaskedContext,
+    isContextConsumer = legacyContext.isContextConsumer,
+    hasContextChanged = legacyContext.hasContextChanged,
+    updater = {
+      isMounted: isMounted,
+      enqueueSetState: function(instance, partialState, callback) {
+        instance = instance._reactInternalFiber;
+        callback = void 0 === callback ? null : callback;
+        var expirationTime = computeExpirationForFiber(instance);
+        insertUpdateIntoFiber(instance, {
+          expirationTime: expirationTime,
+          partialState: partialState,
+          callback: callback,
+          isReplace: !1,
+          isForced: !1,
+          capturedValue: null,
+          next: null
+        });
+        scheduleWork(instance, expirationTime);
+      },
+      enqueueReplaceState: function(instance, state, callback) {
+        instance = instance._reactInternalFiber;
+        callback = void 0 === callback ? null : callback;
+        var expirationTime = computeExpirationForFiber(instance);
+        insertUpdateIntoFiber(instance, {
+          expirationTime: expirationTime,
+          partialState: state,
+          callback: callback,
+          isReplace: !0,
+          isForced: !1,
+          capturedValue: null,
+          next: null
+        });
+        scheduleWork(instance, expirationTime);
+      },
+      enqueueForceUpdate: function(instance, callback) {
+        instance = instance._reactInternalFiber;
+        callback = void 0 === callback ? null : callback;
+        var expirationTime = computeExpirationForFiber(instance);
+        insertUpdateIntoFiber(instance, {
+          expirationTime: expirationTime,
+          partialState: null,
+          callback: callback,
+          isReplace: !1,
+          isForced: !0,
+          capturedValue: null,
+          next: null
+        });
+        scheduleWork(instance, expirationTime);
+      }
+    };
   return {
     adoptClassInstance: adoptClassInstance,
     callGetDerivedStateFromProps: callGetDerivedStateFromProps,
     constructClassInstance: function(workInProgress, props) {
       var ctor = workInProgress.type,
         unmaskedContext = getUnmaskedContext(workInProgress),
-        needsContext =
-          2 === workInProgress.tag && null != workInProgress.type.contextTypes,
+        needsContext = isContextConsumer(workInProgress),
         context = needsContext
           ? getMaskedContext(workInProgress, unmaskedContext)
           : emptyObject;
@@ -2436,10 +2345,7 @@ function ReactFiberClassComponent(
           workInProgress.memoizedState,
           props
         ));
-      needsContext &&
-        ((workInProgress = workInProgress.stateNode),
-        (workInProgress.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext),
-        (workInProgress.__reactInternalMemoizedMaskedChildContext = context));
+      needsContext && cacheContext(workInProgress, unmaskedContext, context);
       return ctor;
     },
     mountClassInstance: function(workInProgress, renderExpirationTime) {
@@ -2539,7 +2445,7 @@ function ReactFiberClassComponent(
         !(
           oldProps !== newProps ||
           oldState !== renderExpirationTime ||
-          didPerformWorkStackCursor.current ||
+          hasContextChanged() ||
           (null !== workInProgress.updateQueue &&
             workInProgress.updateQueue.hasForceUpdate)
         )
@@ -2643,7 +2549,7 @@ function ReactFiberClassComponent(
         !(
           oldProps !== newProps ||
           oldContext !== renderExpirationTime ||
-          didPerformWorkStackCursor.current ||
+          hasContextChanged() ||
           (null !== workInProgress.updateQueue &&
             workInProgress.updateQueue.hasForceUpdate)
         )
@@ -3366,34 +3272,12 @@ function ChildReconciler(shouldTrackSideEffects) {
   };
 }
 var reconcileChildFibers = ChildReconciler(!0),
-  mountChildFibers = ChildReconciler(!1),
-  changedBitsStack = [],
-  currentValueStack = [],
-  stack = [],
-  index$1 = -1;
-function pushProvider(providerFiber) {
-  var context = providerFiber.type.context;
-  index$1 += 1;
-  changedBitsStack[index$1] = context._changedBits;
-  currentValueStack[index$1] = context._currentValue;
-  stack[index$1] = providerFiber;
-  context._currentValue = providerFiber.pendingProps.value;
-  context._changedBits = providerFiber.stateNode;
-}
-function popProvider(providerFiber) {
-  var changedBits = changedBitsStack[index$1],
-    currentValue = currentValueStack[index$1];
-  changedBitsStack[index$1] = null;
-  currentValueStack[index$1] = null;
-  stack[index$1] = null;
-  --index$1;
-  providerFiber = providerFiber.type.context;
-  providerFiber._currentValue = currentValue;
-  providerFiber._changedBits = changedBits;
-}
+  mountChildFibers = ChildReconciler(!1);
 function ReactFiberBeginWork(
   config,
   hostContext,
+  legacyContext,
+  newContext,
   hydrationContext,
   scheduleWork,
   computeExpirationForFiber
@@ -3499,7 +3383,12 @@ function ReactFiberBeginWork(
     changedBits,
     renderExpirationTime
   ) {
-    for (var fiber = workInProgress.child; null !== fiber; ) {
+    var fiber = workInProgress.child;
+    for (
+      null !== fiber && (fiber["return"] = workInProgress);
+      null !== fiber;
+
+    ) {
       switch (fiber.tag) {
         case 12:
           var nextFiber = fiber.stateNode | 0;
@@ -3558,7 +3447,7 @@ function ReactFiberBeginWork(
     var context = workInProgress.type.context,
       newProps = workInProgress.pendingProps,
       oldProps = workInProgress.memoizedProps;
-    if (!didPerformWorkStackCursor.current && oldProps === newProps)
+    if (!hasLegacyContextChanged() && oldProps === newProps)
       return (
         (workInProgress.stateNode = 0),
         pushProvider(workInProgress),
@@ -3645,11 +3534,19 @@ function ReactFiberBeginWork(
     shouldDeprioritizeSubtree = config.shouldDeprioritizeSubtree,
     pushHostContext = hostContext.pushHostContext,
     pushHostContainer = hostContext.pushHostContainer,
+    pushProvider = newContext.pushProvider,
+    getMaskedContext = legacyContext.getMaskedContext,
+    getUnmaskedContext = legacyContext.getUnmaskedContext,
+    hasLegacyContextChanged = legacyContext.hasContextChanged,
+    pushLegacyContextProvider = legacyContext.pushContextProvider,
+    pushTopLevelContextObject = legacyContext.pushTopLevelContextObject,
+    invalidateContextProvider = legacyContext.invalidateContextProvider,
     enterHydrationState = hydrationContext.enterHydrationState,
     resetHydrationState = hydrationContext.resetHydrationState,
     tryToClaimNextHydratableInstance =
       hydrationContext.tryToClaimNextHydratableInstance;
   config = ReactFiberClassComponent(
+    legacyContext,
     scheduleWork,
     computeExpirationForFiber,
     function(workInProgress, nextProps) {
@@ -3676,7 +3573,7 @@ function ReactFiberBeginWork(
             pushHostRootContext(workInProgress);
             break;
           case 2:
-            pushContextProvider(workInProgress);
+            pushLegacyContextProvider(workInProgress);
             break;
           case 4:
             pushHostContainer(
@@ -3722,7 +3619,7 @@ function ReactFiberBeginWork(
                     workInProgress.memoizedState,
                     props
                   ))),
-              (props = pushContextProvider(workInProgress)),
+              (props = pushLegacyContextProvider(workInProgress)),
               adoptClassInstance(workInProgress, fn),
               mountClassInstance(workInProgress, renderExpirationTime),
               (current = finishClassComponent(
@@ -3742,7 +3639,7 @@ function ReactFiberBeginWork(
           return (
             (props = workInProgress.type),
             (renderExpirationTime = workInProgress.pendingProps),
-            didPerformWorkStackCursor.current ||
+            hasLegacyContextChanged() ||
             workInProgress.memoizedProps !== renderExpirationTime
               ? ((fn = getUnmaskedContext(workInProgress)),
                 (fn = getMaskedContext(workInProgress, fn)),
@@ -3758,7 +3655,7 @@ function ReactFiberBeginWork(
             current
           );
         case 2:
-          props = pushContextProvider(workInProgress);
+          props = pushLegacyContextProvider(workInProgress);
           null === current
             ? null === workInProgress.stateNode
               ? (constructClassInstance(
@@ -3840,7 +3737,7 @@ function ReactFiberBeginWork(
             updateQueue = workInProgress.memoizedProps;
             fn = workInProgress.pendingProps;
             unmaskedContext = null !== current ? current.memoizedProps : null;
-            if (!didPerformWorkStackCursor.current && updateQueue === fn) {
+            if (!hasLegacyContextChanged() && updateQueue === fn) {
               if (
                 (updateQueue =
                   workInProgress.mode & 1 &&
@@ -3882,7 +3779,7 @@ function ReactFiberBeginWork(
         case 7:
           return (
             (props = workInProgress.pendingProps),
-            didPerformWorkStackCursor.current ||
+            hasLegacyContextChanged() ||
               workInProgress.memoizedProps !== props ||
               (props = workInProgress.memoizedProps),
             (fn = props.children),
@@ -3912,8 +3809,7 @@ function ReactFiberBeginWork(
               workInProgress.stateNode.containerInfo
             ),
             (props = workInProgress.pendingProps),
-            didPerformWorkStackCursor.current ||
-            workInProgress.memoizedProps !== props
+            hasLegacyContextChanged() || workInProgress.memoizedProps !== props
               ? (null === current
                   ? (workInProgress.child = reconcileChildFibers(
                       workInProgress,
@@ -3944,7 +3840,7 @@ function ReactFiberBeginWork(
         case 10:
           return (
             (renderExpirationTime = workInProgress.pendingProps),
-            didPerformWorkStackCursor.current ||
+            hasLegacyContextChanged() ||
             workInProgress.memoizedProps !== renderExpirationTime
               ? (reconcileChildren(
                   current,
@@ -3962,7 +3858,7 @@ function ReactFiberBeginWork(
         case 11:
           return (
             (renderExpirationTime = workInProgress.pendingProps.children),
-            didPerformWorkStackCursor.current ||
+            hasLegacyContextChanged() ||
             (null !== renderExpirationTime &&
               workInProgress.memoizedProps !== renderExpirationTime)
               ? (reconcileChildren(
@@ -3992,7 +3888,7 @@ function ReactFiberBeginWork(
             props = fn._currentValue;
             var changedBits = fn._changedBits;
             if (
-              didPerformWorkStackCursor.current ||
+              hasLegacyContextChanged() ||
               0 !== changedBits ||
               updateQueue !== unmaskedContext
             ) {
@@ -4032,7 +3928,13 @@ function ReactFiberBeginWork(
     }
   };
 }
-function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
+function ReactFiberCompleteWork(
+  config,
+  hostContext,
+  legacyContext,
+  newContext,
+  hydrationContext
+) {
   function markUpdate(workInProgress) {
     workInProgress.effectTag |= 4;
   }
@@ -4046,6 +3948,9 @@ function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
     popHostContext = hostContext.popHostContext,
     getHostContext = hostContext.getHostContext,
     popHostContainer = hostContext.popHostContainer,
+    popLegacyContextProvider = legacyContext.popContextProvider,
+    popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject,
+    popProvider = newContext.popProvider,
     prepareToHydrateHostInstance =
       hydrationContext.prepareToHydrateHostInstance,
     prepareToHydrateHostTextInstance =
@@ -4074,7 +3979,7 @@ function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
           return null;
         case 2:
           return (
-            popContextProvider(workInProgress),
+            popLegacyContextProvider(workInProgress),
             (current = workInProgress.stateNode),
             (newProps = workInProgress.updateQueue),
             null !== newProps &&
@@ -4087,8 +3992,7 @@ function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
           );
         case 3:
           popHostContainer(workInProgress);
-          pop(didPerformWorkStackCursor, workInProgress);
-          pop(contextStackCursor, workInProgress);
+          popTopLevelLegacyContextObject(workInProgress);
           newProps = workInProgress.stateNode;
           newProps.pendingContext &&
             ((newProps.context = newProps.pendingContext),
@@ -4304,11 +4208,16 @@ function ReactFiberCompleteWork(config, hostContext, hydrationContext) {
 }
 function ReactFiberUnwindWork(
   hostContext,
+  legacyContext,
+  newContext,
   scheduleWork,
   isAlreadyFailedLegacyErrorBoundary
 ) {
   var popHostContainer = hostContext.popHostContainer,
-    popHostContext = hostContext.popHostContext;
+    popHostContext = hostContext.popHostContext,
+    popLegacyContextProvider = legacyContext.popContextProvider,
+    popTopLevelLegacyContextObject = legacyContext.popTopLevelContextObject,
+    popProvider = newContext.popProvider;
   return {
     throwException: function(returnFiber, sourceFiber, rawValue) {
       sourceFiber.effectTag |= 512;
@@ -4352,7 +4261,7 @@ function ReactFiberUnwindWork(
     unwindWork: function(workInProgress) {
       switch (workInProgress.tag) {
         case 2:
-          popContextProvider(workInProgress);
+          popLegacyContextProvider(workInProgress);
           var effectTag = workInProgress.effectTag;
           return effectTag & 1024
             ? ((workInProgress.effectTag = (effectTag & -1025) | 64),
@@ -4361,8 +4270,7 @@ function ReactFiberUnwindWork(
         case 3:
           return (
             popHostContainer(workInProgress),
-            pop(didPerformWorkStackCursor, workInProgress),
-            pop(contextStackCursor, workInProgress),
+            popTopLevelLegacyContextObject(workInProgress),
             (effectTag = workInProgress.effectTag),
             effectTag & 1024
               ? ((workInProgress.effectTag = (effectTag & -1025) | 64),
@@ -4378,6 +4286,25 @@ function ReactFiberUnwindWork(
         default:
           return null;
       }
+    },
+    unwindInterruptedWork: function(interruptedWork) {
+      switch (interruptedWork.tag) {
+        case 2:
+          popLegacyContextProvider(interruptedWork);
+          break;
+        case 3:
+          popHostContainer(interruptedWork);
+          popTopLevelLegacyContextObject(interruptedWork);
+          break;
+        case 5:
+          popHostContext(interruptedWork);
+          break;
+        case 4:
+          popHostContainer(interruptedWork);
+          break;
+        case 13:
+          popProvider(interruptedWork);
+      }
     }
   };
 }
@@ -4819,7 +4746,7 @@ function ReactFiberCommitWork(
   };
 }
 var NO_CONTEXT = {};
-function ReactFiberHostContext(config) {
+function ReactFiberHostContext(config, stack) {
   function requiredContext(c) {
     invariant(
       c !== NO_CONTEXT,
@@ -4828,10 +4755,13 @@ function ReactFiberHostContext(config) {
     return c;
   }
   var getChildHostContext = config.getChildHostContext,
-    getRootHostContext = config.getRootHostContext,
-    contextStackCursor = { current: NO_CONTEXT },
-    contextFiberStackCursor = { current: NO_CONTEXT },
-    rootInstanceStackCursor = { current: NO_CONTEXT };
+    getRootHostContext = config.getRootHostContext;
+  config = stack.createCursor;
+  var push = stack.push,
+    pop = stack.pop,
+    contextStackCursor = config(NO_CONTEXT),
+    contextFiberStackCursor = config(NO_CONTEXT),
+    rootInstanceStackCursor = config(NO_CONTEXT);
   return {
     getHostContext: function() {
       return requiredContext(contextStackCursor.current);
@@ -4861,10 +4791,6 @@ function ReactFiberHostContext(config) {
       context !== rootInstance &&
         (push(contextFiberStackCursor, fiber, fiber),
         push(contextStackCursor, rootInstance, fiber));
-    },
-    resetHostContainer: function() {
-      contextStackCursor.current = NO_CONTEXT;
-      rootInstanceStackCursor.current = NO_CONTEXT;
     }
   };
 }
@@ -5024,22 +4950,198 @@ function ReactFiberHydrationContext(config) {
     }
   };
 }
-function ReactFiberScheduler(config) {
-  function resetContextStack() {
-    for (; -1 < index; ) (valueStack[index] = null), index--;
+function ReactFiberLegacyContext(stack) {
+  function cacheContext(workInProgress, unmaskedContext, maskedContext) {
+    workInProgress = workInProgress.stateNode;
+    workInProgress.__reactInternalMemoizedUnmaskedChildContext = unmaskedContext;
+    workInProgress.__reactInternalMemoizedMaskedChildContext = maskedContext;
+  }
+  function isContextProvider(fiber) {
+    return 2 === fiber.tag && null != fiber.type.childContextTypes;
+  }
+  function processChildContext(fiber, parentContext) {
+    var instance = fiber.stateNode,
+      childContextTypes = fiber.type.childContextTypes;
+    if ("function" !== typeof instance.getChildContext) return parentContext;
+    instance = instance.getChildContext();
+    for (var contextKey in instance)
+      invariant(
+        contextKey in childContextTypes,
+        '%s.getChildContext(): key "%s" is not defined in childContextTypes.',
+        getComponentName(fiber) || "Unknown",
+        contextKey
+      );
+    return Object.assign({}, parentContext, instance);
+  }
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop,
+    contextStackCursor = createCursor(emptyObject),
+    didPerformWorkStackCursor = createCursor(!1),
     previousContext = emptyObject;
-    contextStackCursor.current = emptyObject;
-    didPerformWorkStackCursor.current = !1;
-    resetHostContainer();
-    for (var i = index$1; -1 < i; i--) {
-      var context = stack[i].type.context;
-      context._currentValue = context._defaultValue;
-      context._changedBits = 0;
-      changedBitsStack[i] = null;
-      currentValueStack[i] = null;
-      stack[i] = null;
+  return {
+    getUnmaskedContext: function(workInProgress) {
+      return isContextProvider(workInProgress)
+        ? previousContext
+        : contextStackCursor.current;
+    },
+    cacheContext: cacheContext,
+    getMaskedContext: function(workInProgress, unmaskedContext) {
+      var contextTypes = workInProgress.type.contextTypes;
+      if (!contextTypes) return emptyObject;
+      var instance = workInProgress.stateNode;
+      if (
+        instance &&
+        instance.__reactInternalMemoizedUnmaskedChildContext === unmaskedContext
+      )
+        return instance.__reactInternalMemoizedMaskedChildContext;
+      var context = {},
+        key;
+      for (key in contextTypes) context[key] = unmaskedContext[key];
+      instance && cacheContext(workInProgress, unmaskedContext, context);
+      return context;
+    },
+    hasContextChanged: function() {
+      return didPerformWorkStackCursor.current;
+    },
+    isContextConsumer: function(fiber) {
+      return 2 === fiber.tag && null != fiber.type.contextTypes;
+    },
+    isContextProvider: isContextProvider,
+    popContextProvider: function(fiber) {
+      isContextProvider(fiber) &&
+        (pop(didPerformWorkStackCursor, fiber), pop(contextStackCursor, fiber));
+    },
+    popTopLevelContextObject: function(fiber) {
+      pop(didPerformWorkStackCursor, fiber);
+      pop(contextStackCursor, fiber);
+    },
+    pushTopLevelContextObject: function(fiber, context, didChange) {
+      invariant(
+        null == contextStackCursor.cursor,
+        "Unexpected context found on stack. This error is likely caused by a bug in React. Please file an issue."
+      );
+      push(contextStackCursor, context, fiber);
+      push(didPerformWorkStackCursor, didChange, fiber);
+    },
+    processChildContext: processChildContext,
+    pushContextProvider: function(workInProgress) {
+      if (!isContextProvider(workInProgress)) return !1;
+      var instance = workInProgress.stateNode;
+      instance =
+        (instance && instance.__reactInternalMemoizedMergedChildContext) ||
+        emptyObject;
+      previousContext = contextStackCursor.current;
+      push(contextStackCursor, instance, workInProgress);
+      push(
+        didPerformWorkStackCursor,
+        didPerformWorkStackCursor.current,
+        workInProgress
+      );
+      return !0;
+    },
+    invalidateContextProvider: function(workInProgress, didChange) {
+      var instance = workInProgress.stateNode;
+      invariant(
+        instance,
+        "Expected to have an instance by this point. This error is likely caused by a bug in React. Please file an issue."
+      );
+      if (didChange) {
+        var mergedContext = processChildContext(
+          workInProgress,
+          previousContext
+        );
+        instance.__reactInternalMemoizedMergedChildContext = mergedContext;
+        pop(didPerformWorkStackCursor, workInProgress);
+        pop(contextStackCursor, workInProgress);
+        push(contextStackCursor, mergedContext, workInProgress);
+      } else pop(didPerformWorkStackCursor, workInProgress);
+      push(didPerformWorkStackCursor, didChange, workInProgress);
+    },
+    findCurrentUnmaskedContext: function(fiber) {
+      for (
+        invariant(
+          2 === isFiberMountedImpl(fiber) && 2 === fiber.tag,
+          "Expected subtree parent to be a mounted class component. This error is likely caused by a bug in React. Please file an issue."
+        );
+        3 !== fiber.tag;
+
+      ) {
+        if (isContextProvider(fiber))
+          return fiber.stateNode.__reactInternalMemoizedMergedChildContext;
+        fiber = fiber["return"];
+        invariant(
+          fiber,
+          "Found unexpected detached subtree parent. This error is likely caused by a bug in React. Please file an issue."
+        );
+      }
+      return fiber.stateNode.context;
     }
-    index$1 = -1;
+  };
+}
+function ReactFiberNewContext(stack) {
+  var createCursor = stack.createCursor,
+    push = stack.push,
+    pop = stack.pop,
+    providerCursor = createCursor(null),
+    valueCursor = createCursor(null),
+    changedBitsCursor = createCursor(0);
+  return {
+    pushProvider: function(providerFiber) {
+      var context = providerFiber.type.context;
+      push(changedBitsCursor, context._changedBits, providerFiber);
+      push(valueCursor, context._currentValue, providerFiber);
+      push(providerCursor, providerFiber, providerFiber);
+      context._currentValue = providerFiber.pendingProps.value;
+      context._changedBits = providerFiber.stateNode;
+    },
+    popProvider: function(providerFiber) {
+      var changedBits = changedBitsCursor.current,
+        currentValue = valueCursor.current;
+      pop(providerCursor, providerFiber);
+      pop(valueCursor, providerFiber);
+      pop(changedBitsCursor, providerFiber);
+      providerFiber = providerFiber.type.context;
+      providerFiber._currentValue = currentValue;
+      providerFiber._changedBits = changedBits;
+    }
+  };
+}
+function ReactFiberStack() {
+  var valueStack = [],
+    index = -1;
+  return {
+    createCursor: function(defaultValue) {
+      return { current: defaultValue };
+    },
+    isEmpty: function() {
+      return -1 === index;
+    },
+    pop: function(cursor) {
+      0 > index ||
+        ((cursor.current = valueStack[index]),
+        (valueStack[index] = null),
+        index--);
+    },
+    push: function(cursor, value) {
+      index++;
+      valueStack[index] = cursor.current;
+      cursor.current = value;
+    },
+    checkThatStackIsEmpty: function() {},
+    resetStackAfterFatalErrorInDev: function() {}
+  };
+}
+function ReactFiberScheduler(config) {
+  function resetStack() {
+    if (null !== nextUnitOfWork)
+      for (
+        var interruptedWork = nextUnitOfWork["return"];
+        null !== interruptedWork;
+
+      )
+        unwindInterruptedWork(interruptedWork),
+          (interruptedWork = interruptedWork["return"]);
     nextRoot = null;
     nextRenderExpirationTime = 0;
     nextUnitOfWork = null;
@@ -5145,7 +5247,7 @@ function ReactFiberScheduler(config) {
       root !== nextRoot ||
       null === nextUnitOfWork
     )
-      resetContextStack(),
+      resetStack(),
         (nextRoot = root),
         (nextRenderExpirationTime = expirationTime),
         (nextUnitOfWork = createWorkInProgress(
@@ -5275,7 +5377,7 @@ function ReactFiberScheduler(config) {
             !isWorking &&
               0 !== nextRenderExpirationTime &&
               expirationTime < nextRenderExpirationTime &&
-              resetContextStack();
+              resetStack();
             (nextRoot === root && isWorking) ||
               requestWork(root, expirationTime);
             nestedUpdateCount > NESTED_UPDATE_LIMIT &&
@@ -5619,25 +5721,37 @@ function ReactFiberScheduler(config) {
     nextFlushedRoot.remainingExpirationTime = 0;
     hasUnhandledError || ((hasUnhandledError = !0), (unhandledError = error));
   }
-  var hostContext = ReactFiberHostContext(config),
-    hydrationContext = ReactFiberHydrationContext(config),
-    resetHostContainer = hostContext.resetHostContainer,
+  var stack = ReactFiberStack(),
+    hostContext = ReactFiberHostContext(config, stack),
+    legacyContext = ReactFiberLegacyContext(stack);
+  stack = ReactFiberNewContext(stack);
+  var hydrationContext = ReactFiberHydrationContext(config),
     beginWork = ReactFiberBeginWork(
       config,
       hostContext,
+      legacyContext,
+      stack,
       hydrationContext,
       scheduleWork,
       computeExpirationForFiber
     ).beginWork,
-    completeWork = ReactFiberCompleteWork(config, hostContext, hydrationContext)
-      .completeWork;
+    completeWork = ReactFiberCompleteWork(
+      config,
+      hostContext,
+      legacyContext,
+      stack,
+      hydrationContext
+    ).completeWork;
   hostContext = ReactFiberUnwindWork(
     hostContext,
+    legacyContext,
+    stack,
     scheduleWork,
     isAlreadyFailedLegacyErrorBoundary
   );
   var throwException = hostContext.throwException,
-    unwindWork = hostContext.unwindWork;
+    unwindWork = hostContext.unwindWork,
+    unwindInterruptedWork = hostContext.unwindInterruptedWork;
   hostContext = ReactFiberCommitWork(
     config,
     onCommitPhaseError,
@@ -5796,7 +5910,8 @@ function ReactFiberScheduler(config) {
       result <= lastUniqueAsyncExpiration &&
         (result = lastUniqueAsyncExpiration + 1);
       return (lastUniqueAsyncExpiration = result);
-    }
+    },
+    legacyContext: legacyContext
   };
 }
 function ReactFiberReconciler$1(config) {
@@ -5811,27 +5926,7 @@ function ReactFiberReconciler$1(config) {
     currentTime = container.current;
     if (parentComponent) {
       parentComponent = parentComponent._reactInternalFiber;
-      var parentContext;
-      b: {
-        invariant(
-          2 === isFiberMountedImpl(parentComponent) &&
-            2 === parentComponent.tag,
-          "Expected subtree parent to be a mounted class component. This error is likely caused by a bug in React. Please file an issue."
-        );
-        for (parentContext = parentComponent; 3 !== parentContext.tag; ) {
-          if (isContextProvider(parentContext)) {
-            parentContext =
-              parentContext.stateNode.__reactInternalMemoizedMergedChildContext;
-            break b;
-          }
-          parentContext = parentContext["return"];
-          invariant(
-            parentContext,
-            "Found unexpected detached subtree parent. This error is likely caused by a bug in React. Please file an issue."
-          );
-        }
-        parentContext = parentContext.stateNode.context;
-      }
+      var parentContext = findCurrentUnmaskedContext(parentComponent);
       parentComponent = isContextProvider(parentComponent)
         ? processChildContext(parentComponent, parentContext)
         : parentContext;
@@ -5860,7 +5955,11 @@ function ReactFiberReconciler$1(config) {
   config = ReactFiberScheduler(config);
   var recalculateCurrentTime = config.recalculateCurrentTime,
     computeExpirationForFiber = config.computeExpirationForFiber,
-    scheduleWork = config.scheduleWork;
+    scheduleWork = config.scheduleWork,
+    legacyContext = config.legacyContext,
+    findCurrentUnmaskedContext = legacyContext.findCurrentUnmaskedContext,
+    isContextProvider = legacyContext.isContextProvider,
+    processChildContext = legacyContext.processChildContext;
   return {
     createContainer: function(containerInfo, isAsync, hydrate) {
       isAsync = new FiberNode(3, null, null, isAsync ? 3 : 0);
diff --git a/Libraries/Renderer/shims/ReactFabric.js b/Libraries/Renderer/shims/ReactFabric.js
index 4a396c224..6ab336bf1 100644
--- a/Libraries/Renderer/shims/ReactFabric.js
+++ b/Libraries/Renderer/shims/ReactFabric.js
@@ -9,6 +9,8 @@
  */
 'use strict';
 
+const BatchedBridge = require('BatchedBridge');
+
 // TODO @sema: Adjust types
 import type {ReactNativeType} from 'ReactNativeTypes';
 
@@ -20,4 +22,7 @@ if (__DEV__) {
   ReactFabric = require('ReactFabric-prod');
 }
 
+BatchedBridge.registerCallableModule('ReactFabric', ReactFabric);
+
 module.exports = (ReactFabric: ReactNativeType);
+