Revert 157959 "Introduce a new reference graph to SVG*TearOffs."

Source/core/svg/properties/SVGPropertyTearOff.h

 /*
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * 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
@@ skipping 56 matching lines @@
         m_animatedProperty = animatedProperty;
 
         if (m_animatedProperty)
             m_contextElement = m_animatedProperty->contextElement();
     }
 
     SVGElement* contextElement() const
     {
         if (!m_animatedProperty || m_valueIsCopy)
             return 0;
-        ASSERT(m_contextElement);
-        return m_contextElement;
+        return m_contextElement.get();
     }
 
     void addChild(WeakPtr<SVGPropertyTearOffBase> child)
     {
         m_childTearOffs.append(child);
     }
 
     virtual void detachWrapper() OVERRIDE
     {
         if (m_valueIsCopy)
@@ skipping 59 matching lines @@
 
     void detachChildren()
     {
         for (Vector<WeakPtr<SVGPropertyTearOffBase> >::iterator iter = m_childTearOffs.begin(); iter != m_childTearOffs.end(); iter++) {
             if (iter->get())
                 iter->get()->detachWrapper();
         }
         m_childTearOffs.clear();
     }
 
-    SVGElement* m_contextElement;
+    RefPtr<SVGElement> m_contextElement;
     SVGAnimatedProperty* m_animatedProperty;
     SVGPropertyRole m_role;
     PropertyType* m_value;
     Vector<WeakPtr<SVGPropertyTearOffBase> > m_childTearOffs;
     bool m_valueIsCopy : 1;
 };
 
 }
 
 #endif // SVGPropertyTearOff_h