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

Source/core/dom/TreeScope.cpp

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 104 matching lines @@
             return true;
     }
     return false;
 }
 
 bool TreeScope::rootNodeHasTreeSharedParent() const
 {
     return rootNode().hasTreeSharedParent();
 }
 
+#if !ENABLE(OILPAN)
 void TreeScope::destroyTreeScopeData()
 {
     m_elementsById.clear();
     m_imageMapsByName.clear();
     m_labelsByForAttribute.clear();
 }
+#endif
 
 void TreeScope::setParentTreeScope(TreeScope& newParentScope)
 {
     // A document node cannot be re-parented.
     ASSERT(!rootNode().isDocumentNode());
 
 #if !ENABLE(OILPAN)
     newParentScope.guardRef();
     if (m_parentTreeScope)
         m_parentTreeScope->guardDeref();
@@ skipping 396 matching lines @@
 
 void TreeScope::trace(Visitor* visitor)
 {
     visitor->trace(m_rootNode);
     visitor->trace(m_document);
     visitor->trace(m_parentTreeScope);
     visitor->trace(m_selection);
 }
 
 } // namespace WebCore