Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/platform/mhtml/MHTMLArchive.cpp

 /*
  * Copyright (C) 2011 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 81 matching lines @@
 
 PassRefPtr<MHTMLArchive> MHTMLArchive::create()
 {
     return adoptRef(new MHTMLArchive);
 }
 
 PassRefPtr<MHTMLArchive> MHTMLArchive::create(const KURL& url, SharedBuffer* data)
 {
     // For security reasons we only load MHTML pages from local URLs.
     if (!SchemeRegistry::shouldTreatURLSchemeAsLocal(url.protocol()))
-        return 0;
+        return nullptr;
 
     MHTMLParser parser(data);
     RefPtr<MHTMLArchive> mainArchive = parser.parseArchive();
     if (!mainArchive)
-        return 0; // Invalid MHTML file.
+        return nullptr; // Invalid MHTML file.
 
     // Since MHTML is a flat format, we need to make all frames aware of all resources.
     for (size_t i = 0; i < parser.frameCount(); ++i) {
         RefPtr<MHTMLArchive> archive = parser.frameAt(i);
         for (size_t j = 1; j < parser.frameCount(); ++j) {
             if (i != j)
                 archive->addSubframeArchive(parser.frameAt(j));
         }
         for (size_t j = 0; j < parser.subResourceCount(); ++j)
             archive->addSubresource(parser.subResourceAt(j));
@@ skipping 107 matching lines @@
     for (Vector<RefPtr<MHTMLArchive> >::iterator it = m_subframeArchives.begin(); it != m_subframeArchives.end(); ++it) {
         if (!clearedArchives->contains(*it)) {
             clearedArchives->append(*it);
             (*it)->clearAllSubframeArchivesImpl(clearedArchives);
         }
     }
     m_subframeArchives.clear();
 }
 
 }