Enable Fabric in logbox

Summary:
This diff enables  Fabric in logbox in the facebook app

changelog: [internal] internal

Reviewed By: JoshuaGross

Differential Revision: D28031255

fbshipit-source-id: 8abc301651ad09e4e48c88961bc7f3b91e6c4ae3

ReactAndroid/src/main/java/com/facebook/react/ReactInstanceManager.java

@@ -318,9 +318,8 @@ public class ReactInstanceManager {
         Activity currentActivity = getCurrentActivity();
         if (currentActivity != null) {
           ReactRootView rootView = new ReactRootView(currentActivity);
-
+          rootView.setIsFabric(ReactFeatureFlags.enableFabricInLogBox);
           rootView.startReactApplication(ReactInstanceManager.this, appKey, null);
-
           return rootView;
         }