Oilpan: Remove guardRef and guardDeref from TreeScope.

Source/core/dom/shadow/ShadowRoot.h

 /*
  * Copyright (C) 2011 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 103 matching lines @@
     ShadowRoot* olderShadowRoot() const { return next(); }
 
     String innerHTML() const;
     void setInnerHTML(const String&, ExceptionState&);
 
     PassRefPtr<Node> cloneNode(bool, ExceptionState&);
     PassRefPtr<Node> cloneNode(ExceptionState& exceptionState) { return cloneNode(true, exceptionState); }
 
     StyleSheetList* styleSheets();
 
+    virtual void trace(Visitor* visitor) OVERRIDE
+    {
+        TreeScope::trace(visitor);
+        DocumentFragment::trace(visitor);
+    }
+
 private:
     ShadowRoot(Document&, ShadowRootType);
     virtual ~ShadowRoot();
 
     virtual void dispose() OVERRIDE;
     virtual void childrenChanged(bool changedByParser, Node* beforeChange, Node* afterChange, int childCountDelta) OVERRIDE;
 
     ShadowRootRareData* ensureShadowRootRareData();
 
     void addChildShadowRoot();
@@ skipping 19 matching lines @@
 {
     return adjustedFocusedElement();
 }
 
 DEFINE_NODE_TYPE_CASTS(ShadowRoot, isShadowRoot());
 DEFINE_TYPE_CASTS(ShadowRoot, TreeScope, treeScope, treeScope->rootNode().isShadowRoot(), treeScope.rootNode().isShadowRoot());
 
 } // namespace
 
 #endif