Update remaining core classes to use OVERRIDE / FINAL when needed

Source/core/platform/mediastream/RTCDataChannelHandler.h

 /*
  * Copyright (C) 2012 Google 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 17 matching lines @@
 #include "core/platform/mediastream/RTCDataChannelHandlerClient.h"
 #include "public/platform/WebRTCDataChannelHandler.h"
 #include "public/platform/WebRTCDataChannelHandlerClient.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassOwnPtr.h"
 
 namespace WebCore {
 
 class RTCDataChannelHandlerClient;
 
-class RTCDataChannelHandler : public blink::WebRTCDataChannelHandlerClient {
+class RTCDataChannelHandler FINAL : public blink::WebRTCDataChannelHandlerClient {
 public:
     static PassOwnPtr<RTCDataChannelHandler> create(blink::WebRTCDataChannelHandler*);
     virtual ~RTCDataChannelHandler();
 
     void setClient(RTCDataChannelHandlerClient*);
 
     String label() const;
 
     // DEPRECATED
     bool isReliable() const;
@@ skipping 19 matching lines @@
 private:
     explicit RTCDataChannelHandler(blink::WebRTCDataChannelHandler*);
 
     OwnPtr<blink::WebRTCDataChannelHandler> m_webHandler;
     RTCDataChannelHandlerClient* m_client;
 };
 
 } // namespace WebCore
 
 #endif // RTCDataChannelHandler_h