[gin] Introduce Wrappable::GetObjectTemplate

mojo/apps/js/bindings/waiting_callback.h

Index: mojo/apps/js/bindings/waiting_callback.h
diff --git a/mojo/apps/js/bindings/waiting_callback.h b/mojo/apps/js/bindings/waiting_callback.h
index 55c9b3e0ad1591c9c8d3b34b8b76be576cda64a0..99e85ed0bf32a428b30233959b7272000781f6c0 100644
--- a/mojo/apps/js/bindings/waiting_callback.h
+++ b/mojo/apps/js/bindings/waiting_callback.h
@@ -21,8 +21,6 @@ class WaitingCallback : public gin::Wrappable<WaitingCallback>,
   static gin::Handle<WaitingCallback> Create(
       v8::Isolate* isolate, v8::Handle<v8::Function> callback);
 
-  static void EnsureRegistered(v8::Isolate* isolate);
-
   BindingsSupport::AsyncWaitID wait_id() const {
     return wait_id_;
   }
@@ -32,6 +30,9 @@ class WaitingCallback : public gin::Wrappable<WaitingCallback>,
   }
 
  private:
+  friend class gin::Wrappable<WaitingCallback>;
+  static v8::Local<v8::ObjectTemplate> GetObjectTemplate(v8::Isolate* isolate);
+
   WaitingCallback(v8::Isolate* isolate, v8::Handle<v8::Function> callback);
   virtual ~WaitingCallback();