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

Source/core/svg/SVGTransformListTearOff.h

 /*
  * Copyright (C) 2014 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 23 matching lines @@
 #include "core/svg/SVGTransformList.h"
 #include "core/svg/SVGTransformTearOff.h"
 #include "core/svg/properties/SVGListPropertyTearOffHelper.h"
 
 namespace WebCore {
 
 class SVGTransformListTearOff FINAL :
     public SVGListPropertyTearOffHelper<SVGTransformListTearOff, SVGTransformList>,
     public ScriptWrappable {
 public:
-    static PassRefPtr<SVGTransformListTearOff> create(PassRefPtr<SVGTransformList> target, SVGElement* contextElement, PropertyIsAnimValType propertyIsAnimVal, const QualifiedName& attributeName = nullQName())
+    static PassRefPtr<SVGTransformListTearOff> create(PassRefPtr<SVGTransformList> target, SVGElement* contextElement, PropertyIsAnimValType propertyIsAnimVal, const QualifiedName& attributeName = QualifiedName::null())
     {
         return adoptRef(new SVGTransformListTearOff(target, contextElement, propertyIsAnimVal, attributeName));
     }
 
     virtual ~SVGTransformListTearOff();
 
     PassRefPtr<SVGTransformTearOff> createSVGTransformFromMatrix(PassRefPtr<SVGMatrixTearOff>) const;
     PassRefPtr<SVGTransformTearOff> consolidate(ExceptionState&);
 
 private:
     SVGTransformListTearOff(PassRefPtr<SVGTransformList>, SVGElement*, PropertyIsAnimValType, const QualifiedName&);
 };
 
 } // namespace WebCore
 
 #endif // SVGTransformListTearOff_h_