Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/rendering/style/BasicShapes.cpp

 /*
  * Copyright (C) 2012 Adobe Systems Incorporated. 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.
@@ skipping 387 matching lines @@
         floatSizeForLengthSize(m_topRightRadius, boundingBox),
         floatSizeForLengthSize(m_bottomLeftRadius, boundingBox),
         floatSizeForLengthSize(m_bottomRightRadius, boundingBox)
     );
 }
 
 PassRefPtr<BasicShape> BasicShapeInset::blend(const BasicShape* other, double) const
 {
     ASSERT(type() == other->type());
     // FIXME: Implement blend for BasicShapeInset.
-    return 0;
+    return nullptr;
 }
 
 bool BasicShapeInset::operator==(const BasicShape& o) const
 {
     if (!isSameType(o))
         return false;
     const BasicShapeInset& other = toBasicShapeInset(o);
     return m_right == other.m_right
         && m_top == other.m_top
         && m_bottom == other.m_bottom
         && m_left == other.m_left
         && m_topLeftRadius == other.m_topLeftRadius
         && m_topRightRadius == other.m_topRightRadius
         && m_bottomRightRadius == other.m_bottomRightRadius
         && m_bottomLeftRadius == other.m_bottomLeftRadius;
 }
 
 }