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..307f5cec4bc458d570d266f497d4efed271b1c6d 100644
--- a/webrtc/audio/audio_state.h
+++ b/webrtc/audio/audio_state.h
@@ -12,6 +12,7 @@
 #define WEBRTC_AUDIO_AUDIO_STATE_H_
 
 #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 +29,8 @@ class AudioState final : public webrtc::AudioState,
   ~AudioState() override;
 
   VoiceEngine* voice_engine();
+
+  rtc::scoped_refptr<AudioMixer> mixer();
   bool typing_noise_detected() const;
 
  private:
@@ -53,6 +56,10 @@ 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