Less lock acquisitions for AudioMixer.

webrtc/modules/audio_mixer/audio_mixer_impl.h

Index: webrtc/modules/audio_mixer/audio_mixer_impl.h
diff --git a/webrtc/modules/audio_mixer/audio_mixer_impl.h b/webrtc/modules/audio_mixer/audio_mixer_impl.h
index 6ddf9ca5e8bde5c6954d458a6cfcdba8a902f9e7..30961960b7a5a5659eaea4b08354e1abc84ce0de 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl.h
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl.h
@@ -132,7 +132,6 @@ class AudioMixerImpl : public AudioMixer {
   int GetOutputAudioLevelFullRange() override;
 
   std::unique_ptr<CriticalSectionWrapper> crit_;
-  std::unique_ptr<CriticalSectionWrapper> cb_crit_;

[kwiberg-webrtc, 2016/08/31 09:10:36]

It's troubling that there aren't lock annotations on the member variables that
tell the compiler what the locks are supposed to protect. To prevent mistakes,
it's probably best to start by adding GUARDED_BY annotations everywhere...

(base/thread_checker.h seems to have corresponding annotations for thread
checkers.)

 
   int32_t id_;