support api 15 (use Handler-backed ui driven).

Summary:
Android API 15 still have 1.5~2.0% distribution (refer: [Dashboard - Android Developer](https://developer.android.com/ndk/guides/standalone_toolchain.html#creating_the_toolchain)).

React Native is a good tec but many companies cannot endure loose their consumer. [Choreographer](https://developer.android.com/reference/android/view/Choreographer.html) triggered UI operation is the only reason that React Native Android sdk use minSdkVersion 16, so we can use a backward solution **only in API 15**: [Handler](https://developer.android.com/reference/android/os/Handler.html).

In this PR, the biggest change is :

- Make core operation of ReactChoreographer to an interface: ReactUIDriver;
- Impl ReactUIDriver by Handler => UIDriverHandlerImpl, refactor ReactChoreographer to UIDriverChoreographerImpl;
- Let UIDriverFactory to choose which one impl would be in use. (Only use handler in api 15).
Closes https://github.com/facebook/react-native/pull/12396

Reviewed By: AaaChiuuu

Differential Revision: D4588399

Pulled By: astreet

fbshipit-source-id: 76408e53664314dd926e6a553cde6bafbd37779e

ReactAndroid/src/main/java/com/facebook/react/uimanager/UIViewOperationQueue.java

@@ -722,8 +722,7 @@ public class UIViewOperationQueue {
       final int reactTag,
       final Callback callback) {
     mOperations.add(
-        new MeasureInWindowOperation(reactTag, callback)
-    );
+        new MeasureInWindowOperation(reactTag, callback));
   }
 
   public void enqueueFindTargetForTouch(
@@ -862,7 +861,7 @@ public class UIViewOperationQueue {
    * Using a Choreographer callback (which runs immediately before traversals), we guarantee we run
    * before the next traversal.
    */
-  private class DispatchUIFrameCallback extends GuardedChoreographerFrameCallback {
+  private class DispatchUIFrameCallback extends GuardedFrameCallback {
 
     private static final int MIN_TIME_LEFT_IN_FRAME_TO_SCHEDULE_MORE_WORK_MS = 8;
     private static final int FRAME_TIME_MS = 16;