Fix virtual/override/final usage in Source/platform/.

Source/platform/mediastream/MediaStreamCenter.h

 /*
  * Copyright 2014 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
@@ skipping 32 matching lines @@
 class AudioSourceProvider;
 class MediaStreamComponent;
 class MediaStreamDescriptor;
 class WebMediaStream;
 class WebMediaStreamCenter;
 class WebMediaStreamTrack;
 
 class PLATFORM_EXPORT MediaStreamCenter final : public WebMediaStreamCenterClient {
     WTF_MAKE_NONCOPYABLE(MediaStreamCenter);
 public:
-    virtual ~MediaStreamCenter();
+    ~MediaStreamCenter() override;
 
     static MediaStreamCenter& instance();
 
     void didCreateMediaStreamTrack(MediaStreamComponent*);
     void didSetMediaStreamTrackEnabled(MediaStreamComponent*);
     bool didStopMediaStreamTrack(MediaStreamComponent*);
     PassOwnPtr<AudioSourceProvider> createWebAudioSourceFromMediaStreamTrack(MediaStreamComponent*);
 
     void didCreateMediaStream(MediaStreamDescriptor*);
     void didCreateMediaStreamAndTracks(MediaStreamDescriptor*);
     bool didAddMediaStreamTrack(MediaStreamDescriptor*, MediaStreamComponent*);
     bool didRemoveMediaStreamTrack(MediaStreamDescriptor*, MediaStreamComponent*);
     void didStopLocalMediaStream(MediaStreamDescriptor*);
 
     // blink::WebMediaStreamCenterClient
-    virtual void stopLocalMediaStream(const WebMediaStream&) override;
+    void stopLocalMediaStream(const WebMediaStream&) override;
 
 private:
     MediaStreamCenter();
 
     OwnPtr<WebMediaStreamCenter> m_private;
 };
 
 } // namespace blink
 
 #endif // MediaStreamCenter_h