Standardize usage of virtual/override/final in media/

media/audio/sounds/audio_stream_handler.cc

Index: media/audio/sounds/audio_stream_handler.cc
diff --git a/media/audio/sounds/audio_stream_handler.cc b/media/audio/sounds/audio_stream_handler.cc
index e57612ed11fda470fa136b1a4b92280a01aad565..ac9c87bcfaf1b98d0560727c545766e2ffae054f 100644
--- a/media/audio/sounds/audio_stream_handler.cc
+++ b/media/audio/sounds/audio_stream_handler.cc
@@ -43,7 +43,7 @@ class AudioStreamHandler::AudioStreamContainer
         delayed_stop_posted_(false),
         wav_audio_(wav_audio) {}
 
-  virtual ~AudioStreamContainer() {
+  ~AudioStreamContainer() override {
     DCHECK(AudioManager::Get()->GetTaskRunner()->BelongsToCurrentThread());
   }
 
@@ -104,8 +104,7 @@ class AudioStreamHandler::AudioStreamContainer
  private:
   // AudioOutputStream::AudioSourceCallback overrides:
   // Following methods could be called from *ANY* thread.
-  virtual int OnMoreData(AudioBus* dest,
-                         uint32 /* total_bytes_delay */) override {
+  int OnMoreData(AudioBus* dest, uint32 /* total_bytes_delay */) override {
     base::AutoLock al(state_lock_);
     size_t bytes_written = 0;
 
@@ -124,7 +123,7 @@ class AudioStreamHandler::AudioStreamContainer
     return dest->frames();
   }
 
-  virtual void OnError(AudioOutputStream* /* stream */) override {
+  void OnError(AudioOutputStream* /* stream */) override {
     LOG(ERROR) << "Error during system sound reproduction.";
   }