Oilpan: move SVG property hierarchy to the heap.

Source/core/svg/SVGClipPathElement.h

 /*
  * Copyright (C) 2004, 2005, 2007, 2008 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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #ifndef SVGClipPathElement_h
 #define SVGClipPathElement_h
 
 #include "core/SVGNames.h"
 #include "core/svg/SVGAnimatedBoolean.h"
 #include "core/svg/SVGAnimatedEnumeration.h"
 #include "core/svg/SVGGraphicsElement.h"
 #include "core/svg/SVGUnitTypes.h"
+#include "platform/heap/Handle.h"
 
 namespace blink {
 
 class RenderObject;
 
 class SVGClipPathElement final : public SVGGraphicsElement {
     DEFINE_WRAPPERTYPEINFO();
 public:
     DECLARE_NODE_FACTORY(SVGClipPathElement);
     SVGAnimatedEnumeration<SVGUnitTypes::SVGUnitType>* clipPathUnits() { return m_clipPathUnits.get(); }
 
     virtual bool supportsFocus() const override { return false; }
 
+    virtual void trace(Visitor*) override;
+
 private:
     explicit SVGClipPathElement(Document&);
 
     virtual bool needsPendingResourceHandling() const override { return false; }
 
     virtual void parseAttribute(const QualifiedName&, const AtomicString&) override;
     virtual void svgAttributeChanged(const QualifiedName&) override;
     virtual void childrenChanged(const ChildrenChange&) override;
 
     virtual RenderObject* createRenderer(RenderStyle*) override;
 
-    RefPtr<SVGAnimatedEnumeration<SVGUnitTypes::SVGUnitType> > m_clipPathUnits;
+    RefPtrWillBeMember<SVGAnimatedEnumeration<SVGUnitTypes::SVGUnitType> > m_clipPathUnits;
 };
 
 } // namespace blink
 
 #endif // SVGClipPathElement_h