Standardize usage of virtual/override/final in media/

media/audio/mac/audio_manager_mac.cc

Index: media/audio/mac/audio_manager_mac.cc
diff --git a/media/audio/mac/audio_manager_mac.cc b/media/audio/mac/audio_manager_mac.cc
index 809c923dc322e85cb179c7b8b726b3b8c53dae8c..b6ecf174ba9ccaae51d30b30fc13276706e6af92 100644
--- a/media/audio/mac/audio_manager_mac.cc
+++ b/media/audio/mac/audio_manager_mac.cc
@@ -236,7 +236,7 @@ class AudioManagerMac::AudioPowerObserver : public base::PowerObserver {
     base::PowerMonitor::Get()->AddObserver(this);
   }
 
-  virtual ~AudioPowerObserver() {
+  ~AudioPowerObserver() override {
     DCHECK(thread_checker_.CalledOnValidThread());
     if (!is_monitoring_)
       return;
@@ -251,12 +251,12 @@ class AudioManagerMac::AudioPowerObserver : public base::PowerObserver {
   }
 
  private:
-  virtual void OnSuspend() override {
+  void OnSuspend() override {
     DCHECK(thread_checker_.CalledOnValidThread());
     is_suspending_ = true;
   }
 
-  virtual void OnResume() override {
+  void OnResume() override {
     DCHECK(thread_checker_.CalledOnValidThread());
     is_suspending_ = false;
     earliest_start_time_ = base::TimeTicks::Now() +