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..6f612ca9abea0ca713efefd23611965ed0080d27 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_impl.h
+++ b/webrtc/modules/audio_mixer/audio_mixer_impl.h
@@ -89,7 +89,8 @@ class AudioMixerImpl : public AudioMixer {
   // Compute what audio sources to mix from audio_source_list_. Ramp in
   // and out. Update mixed status. maxAudioFrameCounter specifies how
   // many participants are allowed to be mixed.
-  AudioFrameList UpdateToMix(size_t maxAudioFrameCounter) const;
+  AudioFrameList UpdateToMix(size_t maxAudioFrameCounter) const
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   // Return the lowest mixing frequency that can be used without having to
   // downsample any audio.
@@ -98,7 +99,8 @@ class AudioMixerImpl : public AudioMixer {
       const MixerAudioSourceList& mixList) const;
 
   // Return the AudioFrames that should be mixed anonymously.
-  void GetAdditionalAudio(AudioFrameList* additionalFramesList) const;
+  void GetAdditionalAudio(AudioFrameList* additionalFramesList) const
+      EXCLUSIVE_LOCKS_REQUIRED(crit_);
 
   // This function returns true if it finds the MixerAudioSource in the
   // specified list of MixerAudioSources.
@@ -132,7 +134,6 @@ class AudioMixerImpl : public AudioMixer {
   int GetOutputAudioLevelFullRange() override;
 
   std::unique_ptr<CriticalSectionWrapper> crit_;

[ivoc, 2016/08/31 14:34:24]

Please also add GUARDED_BY(crit_) to any members that are protected by this
critical section.

[aleloi, 2016/08/31 15:16:21]

Done

-  std::unique_ptr<CriticalSectionWrapper> cb_crit_;
 
   int32_t id_;