NotificationController::clientFrom() should return a reference

Source/modules/notifications/Notification.h

Index: Source/modules/notifications/Notification.h
diff --git a/Source/modules/notifications/Notification.h b/Source/modules/notifications/Notification.h
index 774784f11e4d3f0b7d22ad05ce4be9799ab772e2..6fe35ba1e2d6b01f17483860fc08b8baf72f4165 100644
--- a/Source/modules/notifications/Notification.h
+++ b/Source/modules/notifications/Notification.h
@@ -95,7 +95,7 @@ public:
     void trace(Visitor*) { }
 
 private:
-    Notification(const String& title, ExecutionContext*, NotificationClient*);
+    Notification(const String& title, ExecutionContext*, NotificationClient&);
 
     // Calling show() may start asynchronous operation. If this object has
     // a V8 wrapper, hasPendingActivity() prevents the wrapper from being
@@ -127,7 +127,7 @@ private:
 
     NotificationState m_state;
 
-    NotificationClient* m_client;
+    NotificationClient& m_client;
 
     OwnPtr<AsyncMethodRunner<Notification> > m_asyncRunner;
 };