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

Source/core/svg/SVGTransformTearOff.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 34 matching lines @@
     enum SVGTransformType {
         SVG_TRANSFORM_UNKNOWN = WebCore::SVG_TRANSFORM_UNKNOWN,
         SVG_TRANSFORM_MATRIX = WebCore::SVG_TRANSFORM_MATRIX,
         SVG_TRANSFORM_TRANSLATE = WebCore::SVG_TRANSFORM_TRANSLATE,
         SVG_TRANSFORM_SCALE = WebCore::SVG_TRANSFORM_SCALE,
         SVG_TRANSFORM_ROTATE = WebCore::SVG_TRANSFORM_ROTATE,
         SVG_TRANSFORM_SKEWX = WebCore::SVG_TRANSFORM_SKEWX,
         SVG_TRANSFORM_SKEWY = WebCore::SVG_TRANSFORM_SKEWY,
     };
 
-    static PassRefPtr<SVGTransformTearOff> create(PassRefPtr<SVGTransform> target, SVGElement* contextElement, PropertyIsAnimValType propertyIsAnimVal, const QualifiedName& attributeName = nullQName())
+    static PassRefPtr<SVGTransformTearOff> create(PassRefPtr<SVGTransform> target, SVGElement* contextElement, PropertyIsAnimValType propertyIsAnimVal, const QualifiedName& attributeName = QualifiedName::null())
     {
         return adoptRef(new SVGTransformTearOff(target, contextElement, propertyIsAnimVal, attributeName));
     }
 
     virtual ~SVGTransformTearOff();
 
     unsigned short transformType() { return target()->transformType(); }
     SVGMatrixTearOff* matrix();
     float angle() { return target()->angle(); }
 
     void setMatrix(PassRefPtr<SVGMatrixTearOff>, ExceptionState&);
     void setTranslate(float tx, float ty, ExceptionState&);
     void setScale(float sx, float sy, ExceptionState&);
     void setRotate(float angle, float cx, float cy, ExceptionState&);
     void setSkewX(float, ExceptionState&);
     void setSkewY(float, ExceptionState&);
 
 private:
     SVGTransformTearOff(PassRefPtr<SVGTransform>, SVGElement* contextElement, PropertyIsAnimValType, const QualifiedName& attributeName);
 
     RefPtr<SVGMatrixTearOff> m_matrixTearoff;
 };
 
 } // namespace WebCore
 
 #endif // SVGTransformTearOff_h_