Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/css/CSSPrimitiveValue.cpp

 /*
  * (C) 1999-2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2012 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 855 matching lines @@
         return 0;
     }
 
     return m_value.quad;
 }
 
 PassRefPtrWillBeRawPtr<RGBColor> CSSPrimitiveValue::getRGBColorValue(ExceptionState& exceptionState) const
 {
     if (m_primitiveUnitType != CSS_RGBCOLOR) {
         exceptionState.throwDOMException(InvalidAccessError, "This object is not an RGB color value.");
-        return 0;
+        return nullptr;
     }
 
     // FIMXE: This should not return a new object for each invocation.
     return RGBColor::create(m_value.rgbcolor);
 }
 
 Pair* CSSPrimitiveValue::getPairValue(ExceptionState& exceptionState) const
 {
     if (m_primitiveUnitType != CSS_PAIR) {
         exceptionState.throwDOMException(InvalidAccessError, "This object is not a pair value.");
@@ skipping 391 matching lines @@
     case CSS_SHAPE:
         visitor->trace(m_value.shape);
         break;
     default:
         break;
     }
     CSSValue::traceAfterDispatch(visitor);
 }
 
 } // namespace WebCore