Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/xml/XMLHttpRequest.h

 /*
  *  Copyright (C) 2003, 2006, 2008 Apple Inc. All rights reserved.
  *  Copyright (C) 2005, 2006 Alexey Proskuryakov <ap@nypop.com>
  *  Copyright (C) 2011 Google Inc. All rights reserved.
  *  Copyright (C) 2012 Intel Corporation
  *
  *  This library is free software; you can redistribute it and/or
  *  modify it under the terms of the GNU Lesser General Public
  *  License as published by the Free Software Foundation; either
  *  version 2 of the License, or (at your option) any later version.
@@ skipping 41 matching lines @@
 class TextResourceDecoder;
 class ThreadableLoader;
 
 typedef int ExceptionCode;
 
 class XMLHttpRequest FINAL : public RefCountedWillBeRefCountedGarbageCollected<XMLHttpRequest>, public ScriptWrappable, public XMLHttpRequestEventTarget, private ThreadableLoaderClient, public ActiveDOMObject {
     WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED;
     DECLARE_GC_INFO;
     DEFINE_EVENT_TARGET_REFCOUNTING(RefCountedWillBeRefCountedGarbageCollected<XMLHttpRequest>);
 public:
-    static PassRefPtrWillBeRawPtr<XMLHttpRequest> create(ExecutionContext*, PassRefPtr<SecurityOrigin> = 0);
+    static PassRefPtrWillBeRawPtr<XMLHttpRequest> create(ExecutionContext*, PassRefPtr<SecurityOrigin> = nullptr);
     virtual ~XMLHttpRequest();
 
     // These exact numeric values are important because JS expects them.
     enum State {
         UNSENT = 0,
         OPENED = 1,
         HEADERS_RECEIVED = 2,
         LOADING = 3,
         DONE = 4
     };
@@ skipping 192 matching lines @@
 
     // An enum corresponding to the allowed string values for the responseType attribute.
     ResponseTypeCode m_responseTypeCode;
     AsyncMethodRunner<XMLHttpRequest> m_dropProtectionRunner;
     RefPtr<SecurityOrigin> m_securityOrigin;
 };
 
 } // namespace WebCore
 
 #endif // XMLHttpRequest_h