Changed mixing to be done at the minimal possible frequency.

webrtc/api/audio/audio_mixer.h

Index: webrtc/api/audio/audio_mixer.h
diff --git a/webrtc/api/audio/audio_mixer.h b/webrtc/api/audio/audio_mixer.h
index f786d6c99bc336e6ccf57664eaa5c7acc47f3b3a..7c0591d9f3ec0cd69e862bb1258cc8eb8f256b51 100644
--- a/webrtc/api/audio/audio_mixer.h
+++ b/webrtc/api/audio/audio_mixer.h
@@ -60,11 +60,12 @@ class AudioMixer : public rtc::RefCountInterface {
 
   // Performs mixing by asking registered audio sources for audio. The
   // mixed result is placed in the provided AudioFrame. This method
-  // will only be called from a single thread. The rate and channels
-  // arguments specify the rate and number of channels of the mix
-  // result. All fields in |audio_frame_for_mixing| must be updated.
-  virtual void Mix(int sample_rate_hz,
-                   size_t number_of_channels,
+  // will only be called from a single thread. The channels argument
+  // specifies the number of channels of the mix result. The mixer
+  // should mix at a rate that doesn't cause quality loss of the
+  // sources' audio. All fields in |audio_frame_for_mixing| must be
+  // updated.

[hlundin-webrtc, 2016/10/31 14:14:56]

Will the implementation have to provide the mixed audio in any of the native
rates (8, 16, 32, 48), or can it be any rate?

[aleloi, 2016/10/31 14:35:57]

It must be a native rate, and it must be part of the interface. I've added it in
the next ps.

+  virtual void Mix(size_t number_of_channels,
                    AudioFrame* audio_frame_for_mixing) = 0;
 
  protected: