Oilpan: cleanup based on review comments after removal of TreeShared.

Source/core/svg/SVGUseElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  * Copyright (C) 2011 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012 University of Szeged
  * Copyright (C) 2012 Renata Hodovan <reni@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 804 matching lines @@
 {
     if (!inActiveDocument() || m_needsShadowTreeRecreation)
         return;
     scheduleShadowTreeRecreation();
     invalidateDependentShadowTrees();
 }
 
 void SVGUseElement::invalidateDependentShadowTrees()
 {
     // Recursively invalidate dependent <use> shadow trees
-    const HashSet<SVGElement*>& instances = instancesForElement();
-    const HashSet<SVGElement*>::const_iterator end = instances.end();
-    for (HashSet<SVGElement*>::const_iterator it = instances.begin(); it != end; ++it) {
+    const WillBeHeapHashSet<RawPtrWillBeWeakMember<SVGElement> >& instances = instancesForElement();
+    const WillBeHeapHashSet<RawPtrWillBeWeakMember<SVGElement> >::const_iterator end = instances.end();
+    for (WillBeHeapHashSet<RawPtrWillBeWeakMember<SVGElement> >::const_iterator it = instances.begin(); it != end; ++it) {
         if (SVGUseElement* element = (*it)->correspondingUseElement()) {
             ASSERT(element->inDocument());
             element->invalidateShadowTree();
         }
     }
 }
 
 void SVGUseElement::transferUseAttributesToReplacedElement(SVGElement* from, SVGElement* to) const
 {
     ASSERT(from);
@@ skipping 81 matching lines @@
         return;
 
     if (m_resource)
         m_resource->removeClient(this);
 
     m_resource = resource;
     if (m_resource)
         m_resource->addClient(this);
 }
 
+void SVGUseElement::trace(Visitor* visitor)
+{
+    visitor->trace(m_targetElementInstance);
+    SVGGraphicsElement::trace(visitor);
 }
+
+}