Fix virtual/override/final usage in Source/core/html/.

Source/core/html/HTMLModElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Simon Hausmann <hausmann@kde.org>
  * Copyright (C) 2010 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 18 matching lines @@
 namespace blink {
 
 class HTMLModElement final : public HTMLElement {
     DEFINE_WRAPPERTYPEINFO();
 public:
     DECLARE_ELEMENT_FACTORY_WITH_TAGNAME(HTMLModElement);
 
 private:
     HTMLModElement(const QualifiedName&, Document&);
 
-    virtual bool isURLAttribute(const Attribute&) const override;
-    virtual bool hasLegalLinkAttribute(const QualifiedName&) const override;
-    virtual const QualifiedName& subResourceAttributeName() const override;
+    bool isURLAttribute(const Attribute&) const override;
+    bool hasLegalLinkAttribute(const QualifiedName&) const override;
+    const QualifiedName& subResourceAttributeName() const override;
 };
 
 } // namespace blink
 
 #endif // HTMLModElement_h