[oilpan] The Node hierarchy should have correct accept method chains

Source/core/html/HTMLTemplateElement.h

Index: Source/core/html/HTMLTemplateElement.h
diff --git a/Source/core/html/HTMLTemplateElement.h b/Source/core/html/HTMLTemplateElement.h
index cd749ad577bf790be53e5fe611091e3ec6ff1326..0bdd1f8b9834b2abff250e91beb30ea251247dd2 100644
--- a/Source/core/html/HTMLTemplateElement.h
+++ b/Source/core/html/HTMLTemplateElement.h
@@ -43,13 +43,15 @@ public:
 
     DocumentFragment* content() const;
 
+    virtual void acceptHeapVisitor(Visitor*) const OVERRIDE;
+
 private:
     virtual PassRefPtr<Node> cloneNode(bool deep) OVERRIDE;
     virtual void didMoveToNewDocument(Handle<Document> oldDocument) OVERRIDE;
 
     HTMLTemplateElement(const QualifiedName&, Handle<Document>);
 
-    mutable RefPtr<DocumentFragment> m_content;
+    mutable Member<DocumentFragment> m_content;
 };
 
 const HTMLTemplateElement* toHTMLTemplateElement(const Node*);