Added an empty AudioTransportProxy to AudioState.

webrtc/audio/audio_state.h

Index: webrtc/audio/audio_state.h
diff --git a/webrtc/audio/audio_state.h b/webrtc/audio/audio_state.h
index 31892d04faaa5141b9e25d9486553da4ce101b11..c1af5ab98c03beb57c34eaaacfca95633b3c9378 100644
--- a/webrtc/audio/audio_state.h
+++ b/webrtc/audio/audio_state.h
@@ -11,7 +11,9 @@
 #ifndef WEBRTC_AUDIO_AUDIO_STATE_H_
 #define WEBRTC_AUDIO_AUDIO_STATE_H_
 
+#include "webrtc/api/audio/audio_mixer.h"

[the sun, 2016/11/14 13:50:08]

This include should be in audio_state.h instead, right?

[aleloi, 2016/11/14 14:24:42]

I'm not sure. I think there is a similar relationship between class header and
base class' header as between .cc and related .h. Here's what the style guide
says: 


  You should include all the headers that define the symbols you rely upon <...>
However, any includes present in the related header do not need to be included
again in the related cc

[the sun, 2016/11/14 18:13:24]

Right, so by that logic, since the base class' header relies on AudioMixer and
pulls in the header, there's no need to do it here.

 #include "webrtc/api/call/audio_state.h"
+#include "webrtc/audio/audio_transport_proxy.h"
 #include "webrtc/audio/scoped_voe_interface.h"
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/criticalsection.h"
@@ -28,6 +30,8 @@ class AudioState final : public webrtc::AudioState,
   ~AudioState() override;
 
   VoiceEngine* voice_engine();
+
+  rtc::scoped_refptr<AudioMixer> mixer() const;

[the sun, 2016/11/14 13:50:08]

Remove const - you're returning a non-const pointer to an object we own.

[aleloi, 2016/11/14 14:24:42]

Makes sense! I think it's called logical constness.

   bool typing_noise_detected() const;
 
  private:
@@ -53,6 +57,10 @@ class AudioState final : public webrtc::AudioState,
   // Reference count; implementation copied from rtc::RefCountedObject.
   mutable volatile int ref_count_ = 0;
 
+  // Transports mixed audio from the mixer to the audio device and
+  // recorded audio to the VoE AudioTransport.
+  AudioTransportProxy audio_transport_proxy_;
+
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(AudioState);
 };
 }  // namespace internal