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

Source/core/html/track/WebVTTElement.h

 /*
  * Copyright (C) 2013 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 51 matching lines @@
         DEFINE_STATIC_LOCAL(QualifiedName, voiceAttr, (nullAtom, "voice", nullAtom));
         return voiceAttr;
     }
     
     static const QualifiedName& langAttributeName()
     {
         DEFINE_STATIC_LOCAL(QualifiedName, voiceAttr, (nullAtom, "lang", nullAtom));
         return voiceAttr;
     }
 
+    virtual void acceptHeapVisitor(Visitor*) const OVERRIDE;
+
 private:
     WebVTTElement(const QualifiedName&, Handle<Document>);
     WebVTTElement(WebVTTNodeType, Handle<Document>);
 
     unsigned m_isPastNode : 1;
     unsigned m_webVTTNodeType : 4;
     
     AtomicString m_language;
 };
 
 inline WebVTTElement* toWebVTTElement(Node* node)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!node || node->isWebVTTElement());
     return static_cast<WebVTTElement*>(node);
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toWebVTTElement(const WebVTTElement*);
 
 
 } // namespace WebCore