Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/fetch/Resource.cpp

 /*
     Copyright (C) 1998 Lars Knoll (knoll@mpi-hd.mpg.de)
     Copyright (C) 2001 Dirk Mueller (mueller@kde.org)
     Copyright (C) 2002 Waldo Bastian (bastian@kde.org)
     Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
     Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
 
     This library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public
     License as published by the Free Software Foundation; either
@@ skipping 414 matching lines @@
     if (inCache() && m_inLiveDecodedResourcesList && cacheLiveResourcePriority() != static_cast<unsigned>(priority)) {
         memoryCache()->removeFromLiveDecodedResourcesList(this);
         m_cacheLiveResourcePriority = priority;
         memoryCache()->insertInLiveDecodedResourcesList(this);
         memoryCache()->prune();
     }
 }
 
 void Resource::clearLoader()
 {
-    m_loader = 0;
+    m_loader = nullptr;
 }
 
 void Resource::addClient(ResourceClient* client)
 {
     if (addClientToSet(client))
         didAddClient(client);
 }
 
 void Resource::didAddClient(ResourceClient* c)
 {
@@ skipping 557 matching lines @@
         return "Shader";
     case Resource::ImportResource:
         return "ImportResource";
     }
     ASSERT_NOT_REACHED();
     return "Unknown";
 }
 #endif // !LOG_DISABLED
 
 }