[ReactNative] Batch JS -> Native calls per queue

Summary:
@public

For every call that comes from JS to Native we'd call dispatch_async so the
method would be cllead on the queue/thread it's expecting. This diff
buckets the calls by target queue, dispatches only once to that queue, and then
call all the methods for it inside the same dispatch.

Test Plan: {F22510090}

React/Base/RCTBridge.m

@@ -1379,15 +1379,42 @@ RCT_INNER_BRIDGE_ONLY(_invokeAndProcessModule:(NSString *)module method:(NSStrin
     return;
   }
 
-  // TODO: if we sort the requests by module, we could dispatch once per
-  // module instead of per request, which would reduce the call overhead.
+  NSMapTable *buckets = [[NSMapTable alloc] initWithKeyOptions:NSPointerFunctionsStrongMemory valueOptions:NSPointerFunctionsStrongMemory capacity:_queuesByID.count];
   for (NSUInteger i = 0; i < numRequests; i++) {
-    @autoreleasepool {
-      [self _handleRequestNumber:i
-                        moduleID:[moduleIDs[i] integerValue]
-                        methodID:[methodIDs[i] integerValue]
-                          params:paramsArrays[i]
-                         context:context];
+    id queue = RCTNullIfNil(_queuesByID[moduleIDs[i]]);
+    NSMutableOrderedSet *set = [buckets objectForKey:queue];
+    if (!set) {
+      set = [[NSMutableOrderedSet alloc] init];
+      [buckets setObject:set forKey:queue];
+    }
+    [set addObject:@(i)];
+  }
+
+  for (id queue in buckets) {
+    RCTProfileBeginFlowEvent();
+    dispatch_block_t block = ^{
+      RCTProfileEndFlowEvent();
+      RCTProfileBeginEvent();
+
+      NSOrderedSet *calls = [buckets objectForKey:queue];
+      @autoreleasepool {
+        for (NSNumber *indexObj in calls) {
+          NSUInteger index = indexObj.unsignedIntegerValue;
+          [self _handleRequestNumber:index
+                            moduleID:[moduleIDs[index] integerValue]
+                            methodID:[methodIDs[index] integerValue]
+                              params:paramsArrays[index]
+                             context:context];
+        }
+      }
+
+      RCTProfileEndEvent(RCTCurrentThreadName(), @"objc_call,dispatch_async", @{ @"calls": @(calls.count) });
+    };
+
+    if (queue == (id)kCFNull) {
+      [_javaScriptExecutor executeBlockOnJavaScriptQueue:block];
+    } else {
+      dispatch_async(queue, block);
     }
   }
 
@@ -1407,8 +1434,6 @@ RCT_INNER_BRIDGE_ONLY(_invokeAndProcessModule:(NSString *)module method:(NSStrin
                       params:(NSArray *)params
                      context:(NSNumber *)context
 {
-  RCTAssertJSThread();
-
   if (!self.isValid) {
     return NO;
   }
@@ -1426,6 +1451,8 @@ RCT_INNER_BRIDGE_ONLY(_invokeAndProcessModule:(NSString *)module method:(NSStrin
     return NO;
   }
 
+  RCTProfileBeginEvent();
+
   RCTModuleMethod *method = methods[methodID];
 
   // Look up module
@@ -1435,36 +1462,22 @@ RCT_INNER_BRIDGE_ONLY(_invokeAndProcessModule:(NSString *)module method:(NSStrin
     return NO;
   }
 
-  RCTProfileBeginFlowEvent();
-  __weak RCTBatchedBridge *weakSelf = self;
-  [self dispatchBlock:^{
-    RCTProfileEndFlowEvent();
-    RCTProfileBeginEvent();
-    RCTBatchedBridge *strongSelf = weakSelf;
-
-    if (!strongSelf.isValid) {
-      // strongSelf has been invalidated since the dispatch_async call and this
-      // invocation should not continue.
-      return;
+  @try {
+    [method invokeWithBridge:self module:module arguments:params context:context];
+  }
+  @catch (NSException *exception) {
+    RCTLogError(@"Exception thrown while invoking %@ on target %@ with params %@: %@", method.JSMethodName, module, params, exception);
+    if (!RCT_DEBUG && [exception.name rangeOfString:@"Unhandled JS Exception"].location != NSNotFound) {
+      @throw exception;
     }
+  }
 
-    @try {
-      [method invokeWithBridge:strongSelf module:module arguments:params context:context];
-    }
-    @catch (NSException *exception) {
-      RCTLogError(@"Exception thrown while invoking %@ on target %@ with params %@: %@", method.JSMethodName, module, params, exception);
-      if (!RCT_DEBUG && [exception.name rangeOfString:@"Unhandled JS Exception"].location != NSNotFound) {
-        @throw exception;
-      }
-    }
-
-    RCTProfileEndEvent(@"Invoke callback", @"objc_call", @{
-      @"module": method.moduleClassName,
-      @"method": method.JSMethodName,
-      @"selector": NSStringFromSelector(method.selector),
-      @"args": RCTJSONStringify(params ?: [NSNull null], NULL),
-    });
-  } forModuleID:@(moduleID)];
+  RCTProfileEndEvent(@"Invoke callback", @"objc_call", @{
+    @"module": method.moduleClassName,
+    @"method": method.JSMethodName,
+    @"selector": NSStringFromSelector(method.selector),
+    @"args": RCTJSONStringify(params ?: [NSNull null], NULL),
+  });
 
   return YES;
 }

React/Base/RCTUtils.h

@@ -57,3 +57,6 @@ RCT_EXTERN BOOL RCTRunningInTestEnvironment(void);
 
 // Return YES if image has an alpha component
 RCT_EXTERN BOOL RCTImageHasAlpha(CGImageRef image);
+
+RCT_EXTERN id RCTNullIfNil(id value);
+RCT_EXTERN id RCTNilIfNull(id value);

React/Base/RCTUtils.m

@@ -281,3 +281,13 @@ BOOL RCTImageHasAlpha(CGImageRef image)
       return YES;
   }
 }
+
+id RCTNullIfNil(id value)
+{
+  return value ?: (id)kCFNull;
+}
+
+id RCTNilIfNull(id value)
+{
+  return value == (id)kCFNull ? nil : value;
+}