message: webrtc::AudioSendStream: Add lock annotation to audio_level_
  This is a follow-up CL to
  Cr-Commit-Position: refs/heads/master@{#31638}
diff: @@ -170,7 +170,7 @@ class AudioSendStream final : public webrtc::AudioSendStream,
  mutable Mutex audio_level_lock_;
  // Keeps track of audio level, total audio energy and total samples duration.
  // https://w3c.github.io/webrtc-stats/#dom-rtcaudiohandlerstats-totalaudioenergy
  - webrtc::voe::AudioLevel audio_level_;
  + webrtc::voe::AudioLevel audio_level_ RTC_GUARDED_BY(audio_level_lock_);
  BitrateAllocatorInterface* const bitrate_allocator_
  RTC_GUARDED_BY(worker_queue_);
  