Oilpan: move SVG property hierarchy to the heap.

Source/core/svg/SVGSymbolElement.h

 /*
  * Copyright (C) 2004, 2005 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006 Rob Buis <buis@kde.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 12 matching lines @@
 
 #include "core/svg/SVGAnimatedBoolean.h"
 #include "core/svg/SVGElement.h"
 #include "core/svg/SVGFitToViewBox.h"
 
 namespace blink {
 
 class SVGSymbolElement final : public SVGElement,
                                public SVGFitToViewBox {
     DEFINE_WRAPPERTYPEINFO();
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(SVGSymbolElement);
 public:
     DECLARE_NODE_FACTORY(SVGSymbolElement);
 
+    virtual void trace(Visitor*) override;
+
 private:
     explicit SVGSymbolElement(Document&);
 
     virtual void parseAttribute(const QualifiedName&, const AtomicString&) override;
     virtual void svgAttributeChanged(const QualifiedName&) override;
 
     virtual RenderObject* createRenderer(RenderStyle*) override;
 };
 
 } // namespace blink
 
 #endif // SVGSymbolElement_h