Native Animated - Allow events that are dispatched from any thread

Summary:
Instead of preventing events from working when not on the UI Thread we can just dispatch to it instead.

**Test plan**
Tested manually that animated events still work in RNTester
Closes https://github.com/facebook/react-native/pull/15953

Differential Revision: D5909816

Pulled By: shergin

fbshipit-source-id: 48d02b6aa9f2bc3bcb638e8852fccaac3f205276

Libraries/NativeAnimation/RCTNativeAnimatedModule.m

@@ -239,11 +239,11 @@ RCT_EXPORT_METHOD(removeAnimatedEventFromView:(nonnull NSNumber *)viewTag
 
 - (void)eventDispatcherWillDispatchEvent:(id<RCTEvent>)event
 {
-  // Native animated events only work for events dispatched from the main queue.
-  if (!RCTIsMainQueue()) {
-    return;
-  }
-  return [_nodesManager handleAnimatedEvent:event];
+  // Events can be dispatched from any queue so we have to make sure handleAnimatedEvent
+  // is run from the main queue.
+  RCTExecuteOnMainQueue(^{
+    [self->_nodesManager handleAnimatedEvent:event];
+  });
 }
 
 @end

ReactAndroid/src/main/java/com/facebook/react/animated/NativeAnimatedNodesManager.java

@@ -361,12 +361,22 @@ import javax.annotation.Nullable;
   }
 
   @Override
-  public void onEventDispatch(Event event) {
-    // Only support events dispatched from the UI thread.
-    if (!UiThreadUtil.isOnUiThread()) {
-      return;
+  public void onEventDispatch(final Event event) {
+    // Events can be dispatched from any thread so we have to make sure handleEvent is run from the
+    // UI thread.
+    if (UiThreadUtil.isOnUiThread()) {
+      handleEvent(event);
+    } else {
+      UiThreadUtil.runOnUiThread(new Runnable() {
+        @Override
+        public void run() {
+          handleEvent(event);
+        }
+      });
+    }
   }
 
+  private void handleEvent(Event event) {
     if (!mEventDrivers.isEmpty()) {
       // If the event has a different name in native convert it to it's JS name.
       String eventName = mCustomEventNamesResolver.resolveCustomEventName(event.getEventName());