Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/css/CSSCursorImageValue.cpp

 /*
  * Copyright (C) 2006 Rob Buis <buis@kde.org>
  *           (C) 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2008 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 163 matching lines @@
 
 String CSSCursorImageValue::cachedImageURL()
 {
     if (!m_image || !m_image->isImageResource())
         return String();
     return toStyleFetchedImage(m_image)->cachedImage()->url().string();
 }
 
 void CSSCursorImageValue::clearImageResource()
 {
-    m_image = 0;
+    m_image = nullptr;
     m_accessedImage = false;
 }
 
 void CSSCursorImageValue::removeReferencedElement(SVGElement* element)
 {
     m_referencedElements.remove(element);
 }
 
 bool CSSCursorImageValue::equals(const CSSCursorImageValue& other) const
 {
     return m_hasHotSpot ? other.m_hasHotSpot && m_hotSpot == other.m_hotSpot : !other.m_hasHotSpot
         && compareCSSValuePtr(m_imageValue, other.m_imageValue);
 }
 
 void CSSCursorImageValue::traceAfterDispatch(Visitor* visitor)
 {
     visitor->trace(m_imageValue);
     CSSValue::traceAfterDispatch(visitor);
 }
 
 } // namespace WebCore