Resume LockFreeEventDispatcher from onHostResume

Summary:
Found that after backgrounding `mShouldStop` would always remain true, which prevents events from being dispatched / scheduled.

Changelog: [Internal]

Reviewed By: JoshuaGross

Differential Revision: D34247567

fbshipit-source-id: 63876986dc0cee5e2a73cb4f8a35d90379d9f8ea

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

@@ -125,7 +125,8 @@ public class LockFreeEventDispatcherImpl implements EventDispatcher, LifecycleEv
 
   @Override
   public void onHostResume() {
-    maybePostFrameCallbackFromNonUI();
+    UiThreadUtil.assertOnUiThread();
+    mCurrentFrameCallback.resume();
   }
 
   @Override
@@ -183,6 +184,11 @@ public class LockFreeEventDispatcherImpl implements EventDispatcher, LifecycleEv
       driveEventBeats();
     }
 
+    public void resume() {
+      mShouldStop = false;
+      maybePost();
+    }
+
     public void stop() {
       mShouldStop = true;
     }