Oilpan: Remove guardRef and guardDeref from TreeScope.

Source/core/dom/TreeScope.h

Index: Source/core/dom/TreeScope.h
diff --git a/Source/core/dom/TreeScope.h b/Source/core/dom/TreeScope.h
index 288e2d533ed0c3a1d900ad74aa7d4d6e33a058d9..cc7ab175e91ed390c9c582aeeb35edfd98d19deb 100644
--- a/Source/core/dom/TreeScope.h
+++ b/Source/core/dom/TreeScope.h
@@ -102,6 +102,8 @@ public:
 
     IdTargetObserverRegistry& idTargetObserverRegistry() const { return *m_idTargetObserverRegistry.get(); }
 
+
+#if !ENABLE(OILPAN)
     // Nodes belonging to this scope hold guard references -
     // these are enough to keep the scope from being destroyed, but
     // not enough to keep it from removing its children. This allows a
@@ -137,6 +139,7 @@ public:
         }
 #endif
     }
+#endif
 
     void removedLastRefToScope();
 
@@ -156,6 +159,8 @@ public:
 
     Element* getElementByAccessKey(const String& key) const;
 
+    virtual void trace(Visitor*);
+
 protected:
     TreeScope(ContainerNode&, Document&);
     TreeScope(Document&);
@@ -185,7 +190,7 @@ private:
 
     Node& m_rootNode;
     Document* m_document;
-    TreeScope* m_parentTreeScope;
+    RawPtrWillBeMember<TreeScope> m_parentTreeScope;
     int m_guardRefCount;
 
     OwnPtr<DocumentOrderedMap> m_elementsById;