Standardize usage of virtual/override/final in media/

media/audio/audio_device_thread.cc

Index: media/audio/audio_device_thread.cc
diff --git a/media/audio/audio_device_thread.cc b/media/audio/audio_device_thread.cc
index 98d101874434e1edf0e48cc1d271c637e60ba7af..b9cd00f808faf5dab8d61b6ec1aa54751f37ff00 100644
--- a/media/audio/audio_device_thread.cc
+++ b/media/audio/audio_device_thread.cc
@@ -42,10 +42,10 @@ class AudioDeviceThread::Thread
 
  private:
   friend class base::RefCountedThreadSafe<AudioDeviceThread::Thread>;
-  virtual ~Thread();
+  ~Thread() override;
 
   // Overrides from PlatformThread::Delegate.
-  virtual void ThreadMain() override;
+  void ThreadMain() override;
 
   // Runs the loop that reads from the socket.
   void Run();