Integrate Fabric rendering system with ReactChoreographer

Summary:
This diff moves the dispatching of views to the React Choreographer, this help to sort the mount of views following the order specified in the ReactChoreographer class.
This also enables synchronous and correct order for mounting of views that are dispatched in the UI Thread.

Reviewed By: sahrens

Differential Revision: D13444487

fbshipit-source-id: d8a43f473b07c9ccf7ea3bc9ab90545ec3c9ecee

ReactAndroid/src/main/java/com/facebook/react/uimanager/events/EventDispatcher.java

@@ -23,7 +23,6 @@ import java.util.Comparator;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.atomic.AtomicInteger;
-import javax.annotation.Nullable;
 
 /**
  * Class responsible for dispatching UI events to JS. The main purpose of this class is to act as an