Implement SetWrapperReferenceTo idl attribute within traceWrappers for svg elements

third_party/WebKit/Source/core/svg/properties/SVGPropertyTearOff.h

 /*
  * 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 56 matching lines @@
         m_isReadOnlyProperty = true;
     }
 
     bool isImmutable() const
     {
         return isReadOnlyProperty() || isAnimVal();
     }
 
     virtual void commitChange();
 
-    SVGElement* contextElement()
+    SVGElement* contextElement() const
     {
         return m_contextElement;
     }
 
     const QualifiedName& attributeName()
     {
         return m_attributeName;
     }
 
     void attachToSVGElementAttribute(SVGElement* contextElement, const QualifiedName& attributeName)
@@ skipping 66 matching lines @@
         ASSERT(m_target);
     }
 
 private:
     Member<Property> m_target;
 };
 
 } // namespace blink
 
 #endif // SVGPropertyTearOff_h