Clean up virtual functions in css/

Source/core/css/StyleMedia.h

 /*
  * Copyright (C) 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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
@@ skipping 19 matching lines @@
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/frame/DOMWindowProperty.h"
 #include "platform/heap/Handle.h"
 #include "wtf/RefCounted.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class LocalFrame;
 
-class StyleMedia : public RefCountedWillBeGarbageCollected<StyleMedia>, public DOMWindowProperty, public ScriptWrappable {
+class StyleMedia final : public RefCountedWillBeGarbageCollected<StyleMedia>, public DOMWindowProperty, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(StyleMedia);
 public:
     static PassRefPtrWillBeRawPtr<StyleMedia> create(LocalFrame* frame) { return adoptRefWillBeNoop(new StyleMedia(frame));}
 
     AtomicString type() const;
     bool matchMedium(const String&) const;
 
     virtual void trace(Visitor*) override;
 
 private:
     explicit StyleMedia(LocalFrame*);
 };
 
 } // namespace blink
 
 #endif // StyleMedia_h