Oilpan: move SVG property hierarchy to the heap.

Source/core/svg/SVGViewElement.h

 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2007 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 SVGViewElement_h
 #define SVGViewElement_h
 
 #include "core/SVGNames.h"
 #include "core/svg/SVGAnimatedBoolean.h"
 #include "core/svg/SVGElement.h"
 #include "core/svg/SVGFitToViewBox.h"
 #include "core/svg/SVGStaticStringList.h"
 #include "core/svg/SVGZoomAndPan.h"
+#include "platform/heap/Handle.h"
 
 namespace blink {
 
 class SVGViewElement final : public SVGElement,
                              public SVGFitToViewBox,
                              public SVGZoomAndPan {
     DEFINE_WRAPPERTYPEINFO();
+    WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(SVGViewElement);
 public:
     DECLARE_NODE_FACTORY(SVGViewElement);
 
 #if !ENABLE(OILPAN)
     using SVGElement::ref;
     using SVGElement::deref;
 #endif
 
     SVGStringListTearOff* viewTarget() { return m_viewTarget->tearOff(); }
 
+    virtual void trace(Visitor*) override;
+
 private:
     explicit SVGViewElement(Document&);
 
     virtual void parseAttribute(const QualifiedName&, const AtomicString&) override;
 
     virtual bool rendererIsNeeded(const RenderStyle&) override { return false; }
 
-    RefPtr<SVGStaticStringList> m_viewTarget;
+    RefPtrWillBeMember<SVGStaticStringList> m_viewTarget;
 };
 
 } // namespace blink
 
 #endif // SVGViewElement_h