Standardize usage of virtual/override/final in media/

media/audio/mac/audio_auhal_mac.h

Index: media/audio/mac/audio_auhal_mac.h
diff --git a/media/audio/mac/audio_auhal_mac.h b/media/audio/mac/audio_auhal_mac.h
index 62d0439b23bf97a392fc0b8d0d38761f7b2238c0..fd468ffbed0d1dd2d4b17ea42191a9ff57bf5d4c 100644
--- a/media/audio/mac/audio_auhal_mac.h
+++ b/media/audio/mac/audio_auhal_mac.h
@@ -59,15 +59,15 @@ class AUHALStream : public AudioOutputStream {
               AudioDeviceID device);
   // The dtor is typically called by the AudioManager only and it is usually
   // triggered by calling AudioOutputStream::Close().
-  virtual ~AUHALStream();
+  ~AUHALStream() override;
 
   // Implementation of AudioOutputStream.
-  virtual bool Open() override;
-  virtual void Close() override;
-  virtual void Start(AudioSourceCallback* callback) override;
-  virtual void Stop() override;
-  virtual void SetVolume(double volume) override;
-  virtual void GetVolume(double* volume) override;
+  bool Open() override;
+  void Close() override;
+  void Start(AudioSourceCallback* callback) override;
+  void Stop() override;
+  void SetVolume(double volume) override;
+  void GetVolume(double* volume) override;
 
  private:
   // AUHAL callback.