Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/svg/SVGUseElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  * Copyright (C) 2011 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012 University of Szeged
  * Copyright (C) 2012 Renata Hodovan <reni@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 350 matching lines @@
 }
 
 void SVGUseElement::clearResourceReferences()
 {
     // FIXME: We should try to optimize this, to at least allow partial reclones.
     if (ShadowRoot* shadowTreeRootElement = userAgentShadowRoot())
         shadowTreeRootElement->removeChildren();
 
     if (m_targetElementInstance) {
         m_targetElementInstance->detach();
-        m_targetElementInstance = 0;
+        m_targetElementInstance = nullptr;
     }
 
     m_needsShadowTreeRecreation = false;
     document().unscheduleUseShadowTreeUpdate(*this);
 
     document().accessSVGExtensions()->removeAllTargetReferencesForElement(this);
 }
 
 void SVGUseElement::buildPendingResource()
 {
@@ skipping 599 matching lines @@
 
     if (m_resource)
         m_resource->removeClient(this);
 
     m_resource = resource;
     if (m_resource)
         m_resource->addClient(this);
 }
 
 }