Implement SetWrapperReferenceTo idl attribute within traceWrappers for svg elements

third_party/WebKit/Source/core/svg/SVGAnimatedLength.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 30 matching lines @@
     DEFINE_WRAPPERTYPEINFO();
 public:
     static SVGAnimatedLength* create(SVGElement* contextElement, const QualifiedName& attributeName, SVGLength* initialValue)
     {
         return new SVGAnimatedLength(contextElement, attributeName, initialValue);
     }
 
     void setDefaultValueAsString(const String&);
     SVGParsingError setBaseValueAsString(const String&) override;
 
+    DECLARE_VIRTUAL_TRACE_WRAPPERS();
+
 protected:
     SVGAnimatedLength(SVGElement* contextElement, const QualifiedName& attributeName, SVGLength* initialValue)
         : SVGAnimatedProperty<SVGLength>(contextElement, attributeName, initialValue)
     {
     }
 };
 
 } // namespace blink
 
 #endif // SVGAnimatedLength_h