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/androidTest/java/com/facebook/react/testing/ReactIdleDetectionUtil.java

@@ -14,10 +14,10 @@ import java.util.concurrent.TimeUnit;
 import android.app.Instrumentation;
 import android.os.SystemClock;
 import android.support.test.InstrumentationRegistry;
-import android.view.Choreographer;
 
 import com.facebook.react.bridge.ReactContext;
 import com.facebook.react.bridge.UiThreadUtil;
+import com.facebook.react.modules.core.ChoreographerCompat;
 
 public class ReactIdleDetectionUtil {
 
@@ -56,8 +56,8 @@ public class ReactIdleDetectionUtil {
         new Runnable() {
           @Override
           public void run() {
-            Choreographer.getInstance().postFrameCallback(
-                new Choreographer.FrameCallback() {
+            ChoreographerCompat.getInstance().postFrameCallback(
+                new ChoreographerCompat.FrameCallback() {
 
                   private int frameCount = 0;
 
@@ -67,7 +67,7 @@ public class ReactIdleDetectionUtil {
                     if (frameCount == waitFrameCount) {
                       latch.countDown();
                     } else {
-                      Choreographer.getInstance().postFrameCallback(this);
+                      ChoreographerCompat.getInstance().postFrameCallback(this);
                     }
                   }
                 });