Standardize usage of virtual/override/final in media/

media/audio/null_audio_sink.h

Index: media/audio/null_audio_sink.h
diff --git a/media/audio/null_audio_sink.h b/media/audio/null_audio_sink.h
index 6054a95f95e53383fdb8a72f04a4049199673410..d261602c0ec788d333fa2b16ec15276e0f352fc5 100644
--- a/media/audio/null_audio_sink.h
+++ b/media/audio/null_audio_sink.h
@@ -25,13 +25,13 @@ class MEDIA_EXPORT NullAudioSink
   NullAudioSink(const scoped_refptr<base::SingleThreadTaskRunner>& task_runner);
 
   // AudioRendererSink implementation.
-  virtual void Initialize(const AudioParameters& params,
-                          RenderCallback* callback) override;
-  virtual void Start() override;
-  virtual void Stop() override;
-  virtual void Pause() override;
-  virtual void Play() override;
-  virtual bool SetVolume(double volume) override;
+  void Initialize(const AudioParameters& params,
+                  RenderCallback* callback) override;
+  void Start() override;
+  void Stop() override;
+  void Pause() override;
+  void Play() override;
+  bool SetVolume(double volume) override;
 
   // Enables audio frame hashing.  Must be called prior to Initialize().
   void StartAudioHashForTesting();
@@ -40,7 +40,7 @@ class MEDIA_EXPORT NullAudioSink
   std::string GetAudioHashForTesting();
 
  protected:
-  virtual ~NullAudioSink();
+  ~NullAudioSink() override;
 
  private:
   // Task that periodically calls Render() to consume audio data.