Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/dom/DOMImplementation.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Samuel Weinig (sam@webkit.org)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 175 matching lines @@
         return false;
     }
     return true;
 }
 
 PassRefPtr<DocumentType> DOMImplementation::createDocumentType(const AtomicString& qualifiedName,
     const String& publicId, const String& systemId, ExceptionState& exceptionState)
 {
     AtomicString prefix, localName;
     if (!Document::parseQualifiedName(qualifiedName, prefix, localName, exceptionState))
-        return 0;
+        return nullptr;
 
     return DocumentType::create(&m_document, qualifiedName, publicId, systemId);
 }
 
 DOMImplementation* DOMImplementation::getInterface(const String& /*feature*/)
 {
     return 0;
 }
 
 PassRefPtr<XMLDocument> DOMImplementation::createDocument(const AtomicString& namespaceURI,
@@ skipping 11 matching lines @@
         doc = XMLDocument::create(init);
     }
 
     doc->setSecurityOrigin(m_document.securityOrigin()->isolatedCopy());
     doc->setContextFeatures(m_document.contextFeatures());
 
     RefPtr<Node> documentElement;
     if (!qualifiedName.isEmpty()) {
         documentElement = doc->createElementNS(namespaceURI, qualifiedName, exceptionState);
         if (exceptionState.hadException())
-            return 0;
+            return nullptr;
     }
 
     if (doctype)
         doc->appendChild(doctype);
     if (documentElement)
         doc->appendChild(documentElement.release());
 
     return doc.release();
 }
 
@@ skipping 150 matching lines @@
         return TextDocument::create(init);
     if (type == "image/svg+xml")
         return SVGDocument::create(init);
     if (isXMLMIMEType(type))
         return XMLDocument::create(init);
 
     return HTMLDocument::create(init);
 }
 
 }