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..191d4e8b4eb0cb8a51ccafd452ddb475eb7dc835 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_defines.h
+++ b/webrtc/modules/audio_mixer/audio_mixer_defines.h
@@ -44,21 +44,6 @@ 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();

[the sun, 2016/10/04 20:36:09]

- Remove ctor.
- Make the dtor inline and move to top of class declaration (among the methods).

[aleloi, 2016/10/05 15:18:18]

I don't understand what you mean by moving the dtor to the top. Do you want to
make it public? I think a protected virtual destructor helps documenting that
something is a pure virtual base class.

[the sun, 2016/10/05 19:32:10]

A protected virtual destructor means that the object cannot be deleted using a
MixerAudioSource pointer. I don't think it is up to us to decide here how
someone implementing the interface manages objects, so yes, make the dtor public
and virtual.

But thanks for pushing back - the AudioMixer dtor should indeed be protected,
but only once the interface inherits RefCountInterface. The reason of course
being that it should only be deleted from Release().

[aleloi, 2016/10/06 09:26:12]

I see. Good point!