Add native nav bar with title and button icon

Summary: Add native android nav bar. Title and button info are from FBDynamicNavigationOption. Set through setBarOption.

Reviewed By: achen1

Differential Revision: D9367058

fbshipit-source-id: 0f3f790d2c4d3af97568927993964678bc028bc3

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

@@ -205,14 +205,14 @@ public void invoke(Object... args) {
     };
   }
 
-  private Context getContext() {
+  protected Context getContext() {
     if (mActivity != null) {
       return mActivity;
     }
     return Assertions.assertNotNull(mFragmentActivity);
   }
 
-  private Activity getPlainActivity() {
+  protected Activity getPlainActivity() {
     return ((Activity) getContext());
   }
 }