Fabric JS: allow showing fabric indicator for AppRegistry

Summary: AppRegistry always hides the small fabric indicator. This allows it to be enabled.

Reviewed By: mdvacca

Differential Revision: D14877831

fbshipit-source-id: 4fe3aac13074641049a9298f5a616aea3138ce93

Libraries/ReactNative/AppRegistry.js

@@ -60,6 +60,7 @@ let componentProviderInstrumentationHook: ComponentProviderInstrumentationHook =
 ) => component();
 
 let wrapperComponentProvider: ?WrapperComponentProvider;
+let showFabricIndicator = false;
 
 /**
  * `AppRegistry` is the JavaScript entry point to running all React Native apps.
@@ -71,6 +72,10 @@ const AppRegistry = {
     wrapperComponentProvider = provider;
   },
 
+  enableFabricIndicator(enabled: boolean): void {
+    showFabricIndicator = enabled;
+  },
+
   registerConfig(config: Array<AppConfig>): void {
     config.forEach(appConfig => {
       if (appConfig.run) {
@@ -114,7 +119,7 @@ const AppRegistry = {
           appParameters.rootTag,
           wrapperComponentProvider && wrapperComponentProvider(appParameters),
           appParameters.fabric,
-          false,
+          showFabricIndicator,
           scopedPerformanceLogger,
         );
       },