Made MixerAudioSource a pure interface.

webrtc/modules/audio_mixer/audio_mixer_defines.h

Index: webrtc/modules/audio_mixer/audio_mixer_defines.h
diff --git a/webrtc/modules/audio_mixer/audio_mixer_defines.h b/webrtc/modules/audio_mixer/audio_mixer_defines.h
index 57e7f5027e4bf338843d8e1a3a0a0b48fbd7ef96..7c0dab6cf0fcb8929da40574f928e66e35f4054d 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_defines.h
+++ b/webrtc/modules/audio_mixer/audio_mixer_defines.h
@@ -44,24 +44,7 @@ class MixerAudioSource {
   virtual AudioFrameWithMuted GetAudioFrameWithMuted(int32_t id,
                                                      int sample_rate_hz) = 0;
 
-  // Returns true if the audio source was mixed this mix iteration.
-  bool IsMixed() const;
-
-  // Returns true if the audio source was mixed previous mix
-  // iteration.
-  bool WasMixed() const;
-
-  // Updates the mixed status.
-  int32_t SetIsMixed(bool mixed);
-
-  void ResetMixedStatus();
-
- private:
-  bool is_mixed_;
-
- protected:
-  MixerAudioSource();
-  virtual ~MixerAudioSource();
+  virtual ~MixerAudioSource() = default;

[the sun, 2016/10/06 09:50:31]

nit: it is common to have the ctor/dtor as the first methods in the class
(though I'm not sure if there's a style guide for that)

[aleloi, 2016/10/06 12:17:12]

Done.

 };
 }  // namespace webrtc