AudioMixer interface cleanup suggestions

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..54a6f5b498efc96d6d8e7a16ee5fd6f31113ca15 100644
--- a/webrtc/modules/audio_mixer/audio_mixer_defines.h
+++ b/webrtc/modules/audio_mixer/audio_mixer_defines.h
@@ -8,6 +8,9 @@
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
+// !!!: Remove this file. "_defines" sounds to me like it would either be
+// #define constants/macros, or other constants, but it is not. It defines a
+// mixer source. Confusing.
 #ifndef WEBRTC_MODULES_AUDIO_MIXER_AUDIO_MIXER_DEFINES_H_
 #define WEBRTC_MODULES_AUDIO_MIXER_AUDIO_MIXER_DEFINES_H_
 
@@ -19,6 +22,9 @@
 
 namespace webrtc {
 
+// !!!: Move into audio_mixer.h, rename it AudioMixerSource and make it a
+// pure interface.
+
 // A callback class that all mixer participants must inherit from/implement.
 class MixerAudioSource {
  public:
@@ -30,11 +36,15 @@ class MixerAudioSource {
     kError    // audio_frame will not be used.
   };
 
+  // !!!: Document life expectancy of the AudioFrame* - how long can the client
+  // access it?
   struct AudioFrameWithMuted {
     AudioFrame* audio_frame;
     AudioFrameInfo audio_frame_info;
   };
 
+  // !!!: Get rid of "id"
+
   // The implementation of GetAudioFrameWithMuted should update
   // audio_frame with new audio every time it's called. Implementing
   // classes are allowed to return the same AudioFrame pointer on