Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/rendering/style/StylePendingImage.h

 /*
  * Copyright (C) 2010 Apple Inc. 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 44 matching lines @@
     virtual bool imageHasRelativeWidth() const OVERRIDE { return false; }
     virtual bool imageHasRelativeHeight() const OVERRIDE { return false; }
     virtual void computeIntrinsicDimensions(const RenderObject*, Length& /* intrinsicWidth */ , Length& /* intrinsicHeight */, FloatSize& /* intrinsicRatio */) OVERRIDE { }
     virtual bool usesImageContainerSize() const OVERRIDE { return false; }
     virtual void setContainerSizeForRenderer(const RenderObject*, const IntSize&, float) OVERRIDE { }
     virtual void addClient(RenderObject*) OVERRIDE { }
     virtual void removeClient(RenderObject*) OVERRIDE { }
     virtual PassRefPtr<Image> image(RenderObject*, const IntSize&) const OVERRIDE
     {
         ASSERT_NOT_REACHED();
-        return 0;
+        return nullptr;
     }
     virtual bool knownToBeOpaque(const RenderObject*) const OVERRIDE { return false; }
 
 private:
     StylePendingImage(CSSValue* value)
         : m_value(value)
     {
         m_isPendingImage = true;
     }
 
     CSSValue* m_value; // Not retained; it owns us.
 };
 
 DEFINE_STYLE_IMAGE_TYPE_CASTS(StylePendingImage, isPendingImage());
 
 }
 #endif