Standardize usage of virtual/override/final in media/

media/base/audio_renderer_mixer.h

Index: media/base/audio_renderer_mixer.h
diff --git a/media/base/audio_renderer_mixer.h b/media/base/audio_renderer_mixer.h
index 00197c28e61b2b42c75b04dd3f7d5bb56550356d..35ed484976fdb83ee4975b955c10a5e3a296b131 100644
--- a/media/base/audio_renderer_mixer.h
+++ b/media/base/audio_renderer_mixer.h
@@ -23,7 +23,7 @@ class MEDIA_EXPORT AudioRendererMixer
   AudioRendererMixer(const AudioParameters& input_params,
                      const AudioParameters& output_params,
                      const scoped_refptr<AudioRendererSink>& sink);
-  virtual ~AudioRendererMixer();
+  ~AudioRendererMixer() override;
 
   // Add or remove a mixer input from mixing; called by AudioRendererMixerInput.
   void AddMixerInput(AudioConverter::InputCallback* input);
@@ -41,9 +41,8 @@ class MEDIA_EXPORT AudioRendererMixer
 
  private:
   // AudioRendererSink::RenderCallback implementation.
-  virtual int Render(AudioBus* audio_bus,
-                     int audio_delay_milliseconds) override;
-  virtual void OnRenderError() override;
+  int Render(AudioBus* audio_bus, int audio_delay_milliseconds) override;
+  void OnRenderError() override;
 
   // Output sink for this mixer.
   scoped_refptr<AudioRendererSink> audio_sink_;