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

Source/core/html/PluginDocument.h

 /*
  * Copyright (C) 2006, 2008, 2009 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 32 matching lines @@
 
     Widget* pluginWidget();
     Node* pluginNode();
 
     virtual void detach() OVERRIDE;
 
     void cancelManualPluginLoad();
 
     bool shouldLoadPluginManually() { return m_shouldLoadPluginManually; }
 
+    virtual void acceptHeapVisitor(Visitor*) const OVERRIDE;
+
 private:
     PluginDocument(Frame*, const KURL&);
 
     virtual PassRefPtr<DocumentParser> createParser() OVERRIDE;
     virtual bool isPluginDocument() const OVERRIDE { return true; }    
         
     void setShouldLoadPluginManually(bool loadManually) { m_shouldLoadPluginManually = loadManually; }
 
     bool m_shouldLoadPluginManually;
     RefPtr<Node> m_pluginNode;
@@ skipping 20 matching lines @@
 {
     return toPluginDocument(Handle<const Document>(document));
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toPluginDocument(const PluginDocument*);
     
 }
 
 #endif // PluginDocument_h