Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/loader/NavigationAction.h

 /*
  * Copyright (C) 2006 Apple Computer, 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:
  *
  * 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 23 matching lines @@
 #include "core/loader/NavigationPolicy.h"
 #include "platform/network/ResourceRequest.h"
 #include "platform/weborigin/KURL.h"
 #include "wtf/Forward.h"
 
 namespace WebCore {
 
     class NavigationAction {
     public:
         NavigationAction();
-        NavigationAction(const ResourceRequest&, FrameLoadType = FrameLoadTypeStandard, bool isFormSubmission = false, PassRefPtr<Event> = 0);
+        NavigationAction(const ResourceRequest&, FrameLoadType = FrameLoadTypeStandard, bool isFormSubmission = false, PassRefPtr<Event> = nullptr);
 
         const ResourceRequest& resourceRequest() const { return m_resourceRequest; }
         NavigationType type() const { return m_type; }
         Event* event() const { return m_event.get(); }
         NavigationPolicy policy() const { return m_policy; }
         bool shouldOpenInNewWindow() const { return m_policy != NavigationPolicyCurrentTab; }
 
     private:
         ResourceRequest m_resourceRequest;
         NavigationType m_type;
         RefPtr<Event> m_event;
         NavigationPolicy m_policy;
     };
 
 }
 
 #endif