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

Source/core/html/HTMLUnknownElement.h

 /*
  * Copyright (c) 2011 Code Aurora Forum. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *     * Redistributions of source code must retain the above copyright
  *       notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
  *       copyright notice, this list of conditions and the following
@@ skipping 28 matching lines @@
 public:
     static PassRefPtrWillBeRawPtr<HTMLUnknownElement> create(const QualifiedName& tagName, Document& document)
     {
         return adoptRefWillBeNoop(new HTMLUnknownElement(tagName, document));
     }
 
 private:
     HTMLUnknownElement(const QualifiedName& tagName, Document& document)
         : HTMLElement(tagName, document) { }
 
-    virtual bool isHTMLUnknownElement() const override { return true; }
+    bool isHTMLUnknownElement() const override { return true; }
 };
 
 inline bool isHTMLUnknownElement(const HTMLElement& element)
 {
     return element.isHTMLUnknownElement();
 }
 
 DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(HTMLUnknownElement);
 
 } // namespace blink
 
 #endif // HTMLUnknownElement_h