NotificationController::clientFrom() should return a reference

Source/modules/notifications/Notification.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 77 matching lines @@
     virtual bool dispatchEvent(PassRefPtrWillBeRawPtr<Event>) OVERRIDE FINAL;
     virtual const AtomicString& interfaceName() const OVERRIDE;
 
     // ActiveDOMObject interface.
     virtual void stop() OVERRIDE;
     virtual bool hasPendingActivity() const OVERRIDE;
 
     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
     // collected while m_state is Showing, and so this instance stays alive
     // until the operation completes. Otherwise, you need to hold a ref on this
     // instance until the operation completes.
     void show();
 
     void setDir(const String& dir) { m_dir = dir; }
     void setLang(const String& lang) { m_lang = lang; }
@@ skipping 11 matching lines @@
     KURL m_iconUrl;
 
     enum NotificationState {
         Idle = 0,
         Showing = 1,
         Closed = 2,
     };
 
     NotificationState m_state;
 
-    NotificationClient* m_client;
+    NotificationClient& m_client;
 
     OwnPtr<AsyncMethodRunner<Notification> > m_asyncRunner;
 };
 
 } // namespace WebCore
 
 #endif // Notification_h