Standardize usage of virtual/override/final in media/

media/audio/audio_output_device.cc

Index: media/audio/audio_output_device.cc
diff --git a/media/audio/audio_output_device.cc b/media/audio/audio_output_device.cc
index d18a7648aadcc8106a9270cb8249cebfd5df9c1c..c34d7cc1296e1ba896ea10f61c3a57b4cde3e44c 100644
--- a/media/audio/audio_output_device.cc
+++ b/media/audio/audio_output_device.cc
@@ -23,12 +23,12 @@ class AudioOutputDevice::AudioThreadCallback
                       base::SharedMemoryHandle memory,
                       int memory_length,
                       AudioRendererSink::RenderCallback* render_callback);
-  virtual ~AudioThreadCallback();
+  ~AudioThreadCallback() override;
 
-  virtual void MapSharedMemory() override;
+  void MapSharedMemory() override;
 
   // Called whenever we receive notifications about pending data.
-  virtual void Process(int pending_data) override;
+  void Process(int pending_data) override;
 
  private:
   AudioRendererSink::RenderCallback* render_callback_;