[oilpan]: Avoid refcounting QualifiedName's nullQName when tracing.

Source/core/svg/properties/SVGAnimatedProperty.cpp

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 24 matching lines @@
 
 namespace WebCore {
 
 SVGAnimatedPropertyBase::SVGAnimatedPropertyBase(AnimatedPropertyType type, SVGElement* contextElement, const QualifiedName& attributeName)
     : m_type(type)
     , m_isReadOnly(false)
     , m_contextElement(contextElement)
     , m_attributeName(attributeName)
 {
     ASSERT(m_contextElement);
-    ASSERT(m_attributeName != nullQName());
+    ASSERT(m_attributeName != QualifiedName::null());
     // FIXME: setContextElement should be delayed until V8 wrapper is created.
     // FIXME: oilpan: or we can remove this backref ptr hack in oilpan.
     m_contextElement->setContextElement();
 }
 
 SVGAnimatedPropertyBase::~SVGAnimatedPropertyBase()
 {
 }
 
 void SVGAnimatedPropertyBase::animationEnded()
 {
     synchronizeAttribute();
 }
 
 void SVGAnimatedPropertyBase::synchronizeAttribute()
 {
     AtomicString value(currentValueBase()->valueAsString());
     m_contextElement->setSynchronizedLazyAttribute(m_attributeName, value);
 }
 
 bool SVGAnimatedPropertyBase::isSpecified() const
 {
     return isAnimating() || contextElement()->hasAttribute(attributeName());
 }
 
 } // namespace WebCore