Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/loader/DocumentWriter.cpp

 /*
  * Copyright (C) 2010. Adam Barth. 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 99 matching lines @@
         m_parser->setDecoder(decoder.release());
     }
     // flush() can result replacing DocumentLoader::m_writer.
     RefPtr<DocumentWriter> protectingThis(this);
     m_parser->flush();
 
     if (!m_parser)
         return;
 
     m_parser->finish();
-    m_parser = 0;
+    m_parser = nullptr;
     m_document = 0;
 }
 
 void DocumentWriter::setUserChosenEncoding(const String& charset)
 {
     TextResourceDecoder* decoder = m_parser->decoder();
     if (decoder)
         decoder->setEncoding(charset, TextResourceDecoder::UserChosenEncoding);
 }
 
 void DocumentWriter::setDocumentWasLoadedAsPartOfNavigation()
 {
     ASSERT(m_parser && !m_parser->isStopped());
     m_parser->setDocumentWasLoadedAsPartOfNavigation();
 }
 
 } // namespace WebCore