Standardize usage of virtual/override/final in media/

media/audio/simple_sources.h

Index: media/audio/simple_sources.h
diff --git a/media/audio/simple_sources.h b/media/audio/simple_sources.h
index 98caf2893efd025d612839241e723c07551472ab..7a2176f6bc28788fca658cfd158f1b737d17ac27 100644
--- a/media/audio/simple_sources.h
+++ b/media/audio/simple_sources.h
@@ -19,7 +19,7 @@ class MEDIA_EXPORT SineWaveAudioSource
   // hertz and it has to be less than half of the sampling frequency
   // |sample_freq| or else you will get aliasing.
   SineWaveAudioSource(int channels, double freq, double sample_freq);
-  virtual ~SineWaveAudioSource() {}
+  ~SineWaveAudioSource() override {}
 
   // Return up to |cap| samples of data via OnMoreData().  Use Reset() to
   // allow more data to be served.
@@ -27,9 +27,8 @@ class MEDIA_EXPORT SineWaveAudioSource
   void Reset();
 
   // Implementation of AudioSourceCallback.
-  virtual int OnMoreData(AudioBus* audio_bus,
-                         uint32 total_bytes_delay) override;
-  virtual void OnError(AudioOutputStream* stream) override;
+  int OnMoreData(AudioBus* audio_bus, uint32 total_bytes_delay) override;
+  void OnError(AudioOutputStream* stream) override;
 
   // The number of OnMoreData() and OnError() calls respectively.
   int callbacks() { return callbacks_; }