Standardize usage of virtual/override/final specifiers.

media/audio/alsa/alsa_input.h

Index: media/audio/alsa/alsa_input.h
diff --git a/media/audio/alsa/alsa_input.h b/media/audio/alsa/alsa_input.h
index ef7cb2c6da6100862cacd0abf117be6c955d6601..b04e628aea5153b6c68d0839e9bb199d2bf78122 100644
--- a/media/audio/alsa/alsa_input.h
+++ b/media/audio/alsa/alsa_input.h
@@ -39,17 +39,17 @@ class AlsaPcmInputStream : public AgcAudioStream<AudioInputStream> {
                      const AudioParameters& params,
                      AlsaWrapper* wrapper);
 
-  virtual ~AlsaPcmInputStream();
+  ~AlsaPcmInputStream() override;
 
   // Implementation of AudioInputStream.
-  virtual bool Open() override;
-  virtual void Start(AudioInputCallback* callback) override;
-  virtual void Stop() override;
-  virtual void Close() override;
-  virtual double GetMaxVolume() override;
-  virtual void SetVolume(double volume) override;
-  virtual double GetVolume() override;
-  virtual bool IsMuted() override;
+  bool Open() override;
+  void Start(AudioInputCallback* callback) override;
+  void Stop() override;
+  void Close() override;
+  double GetMaxVolume() override;
+  void SetVolume(double volume) override;
+  double GetVolume() override;
+  bool IsMuted() override;
 
  private:
   // Logs the error and invokes any registered callbacks.