Standardize usage of virtual/override/final in media/

media/audio/virtual_audio_output_stream.h

Index: media/audio/virtual_audio_output_stream.h
diff --git a/media/audio/virtual_audio_output_stream.h b/media/audio/virtual_audio_output_stream.h
index c753975e4dc9af70affcea3d0731ec0d13f68ecc..ef9863e1441d3a19f569083579b1c7d8c226fd50 100644
--- a/media/audio/virtual_audio_output_stream.h
+++ b/media/audio/virtual_audio_output_stream.h
@@ -34,20 +34,20 @@ class MEDIA_EXPORT VirtualAudioOutputStream
                            VirtualAudioInputStream* target,
                            const AfterCloseCallback& after_close_cb);
 
-  virtual ~VirtualAudioOutputStream();
+  ~VirtualAudioOutputStream() override;
 
   // AudioOutputStream:
-  virtual bool Open() override;
-  virtual void Start(AudioSourceCallback* callback) override;
-  virtual void Stop() override;
-  virtual void SetVolume(double volume) override;
-  virtual void GetVolume(double* volume) override;
-  virtual void Close() override;
+  bool Open() override;
+  void Start(AudioSourceCallback* callback) override;
+  void Stop() override;
+  void SetVolume(double volume) override;
+  void GetVolume(double* volume) override;
+  void Close() override;
 
  private:
   // AudioConverter::InputCallback:
-  virtual double ProvideInput(AudioBus* audio_bus,
-                              base::TimeDelta buffer_delay) override;
+  double ProvideInput(AudioBus* audio_bus,
+                      base::TimeDelta buffer_delay) override;
 
   const AudioParameters params_;
   // Pointer to the VirtualAudioInputStream to attach to when Start() is called.