Subtle stopSurface lifecycle change

Summary:
Change lifecycle of stopSurface in a subtle way: mark the surface as stopped in Java first, then in Cxx (currently it happens in Cxx, then Java).

This will cause us / allow us to ignore the final mounting instructions for the Surface, which are all irrelevant since they just have to do with View removal.
We can rely on GC and `unmountReactApplication` to do all of this for us, and save some CPU cycles on stopSurface.

Changelog: [Internal]

Reviewed By: shergin

Differential Revision: D26469741

fbshipit-source-id: a7f81d44c3cb2138f0ab31feb38852910410c638

ReactAndroid/src/main/java/com/facebook/react/fabric/FabricUIManager.java

@@ -280,8 +280,13 @@ public class FabricUIManager implements UIManager, LifecycleEventListener {
   @ThreadConfined(ANY)
   @Override
   public void stopSurface(final int surfaceID) {
-    mBinding.stopSurface(surfaceID);
+    // Mark surfaceId as dead, stop executing mounting instructions
     mMountingManager.stopSurface(surfaceID);
+
+    // Communicate stopSurface to Cxx - causes an empty ShadowTree to be committed,
+    // but all mounting instructions will be ignored because stopSurface was called
+    // on the MountingManager
+    mBinding.stopSurface(surfaceID);
   }
 
   @Override