Remove internalSubset from DocumentType

Source/core/dom/DocumentType.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 22 matching lines @@
 class DocumentType FINAL : public Node {
 public:
     static PassRefPtrWillBeRawPtr<DocumentType> create(Document* document, const String& name, const String& publicId, const String& systemId)
     {
         return adoptRefWillBeRefCountedGarbageCollected(new DocumentType(document, name, publicId, systemId));
     }
 
     const String& name() const { return m_name; }
     const String& publicId() const { return m_publicId; }
     const String& systemId() const { return m_systemId; }
-    const String& internalSubset() const { return m_subset; }
 
 private:
     DocumentType(Document*, const String& name, const String& publicId, const String& systemId);
 
     virtual KURL baseURI() const OVERRIDE;
     virtual String nodeName() const OVERRIDE;
     virtual NodeType nodeType() const OVERRIDE;
     virtual PassRefPtrWillBeRawPtr<Node> cloneNode(bool deep) OVERRIDE;
 
     virtual InsertionNotificationRequest insertedInto(ContainerNode*) OVERRIDE;
     virtual void removedFrom(ContainerNode*) OVERRIDE;
 
     String m_name;
     String m_publicId;
     String m_systemId;
-    String m_subset;
 };
 
 DEFINE_NODE_TYPE_CASTS(DocumentType, isDocumentTypeNode());
 
 } // namespace WebCore
 
 #endif