Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/modules/notifications/DOMWindowNotifications.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 51 matching lines @@
     return *supplement;
 }
 
 NotificationCenter* DOMWindowNotifications::webkitNotifications(DOMWindow& window)
 {
     return DOMWindowNotifications::from(window).webkitNotifications();
 }
 
 void DOMWindowNotifications::willDestroyGlobalObjectInFrame()
 {
-    m_notificationCenter = 0;
+    m_notificationCenter = nullptr;
     DOMWindowProperty::willDestroyGlobalObjectInFrame();
 }
 
 void DOMWindowNotifications::willDetachGlobalObjectFromFrame()
 {
-    m_notificationCenter = 0;
+    m_notificationCenter = nullptr;
     DOMWindowProperty::willDetachGlobalObjectFromFrame();
 }
 
 NotificationCenter* DOMWindowNotifications::webkitNotifications()
 {
     if (!m_window.isCurrentlyDisplayedInFrame())
         return 0;
 
     if (m_notificationCenter)
         return m_notificationCenter.get();
 
     Document* document = m_window.document();
     if (!document)
         return 0;
 
     Page* page = document->page();
     if (!page)
         return 0;
 
     NotificationClient* provider = NotificationController::clientFrom(page);
     if (provider)
         m_notificationCenter = NotificationCenter::create(document, provider);
 
     return m_notificationCenter.get();
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(LEGACY_NOTIFICATIONS)