Support external audio mixer.

webrtc/media/engine/webrtcvoiceengine.cc

Index: webrtc/media/engine/webrtcvoiceengine.cc
diff --git a/webrtc/media/engine/webrtcvoiceengine.cc b/webrtc/media/engine/webrtcvoiceengine.cc
index 96f9ed70d403c6c464cc9b015f83190630a0b331..4931d3d03381e5df0e514cc3633c4b6a513b25c3 100644
--- a/webrtc/media/engine/webrtcvoiceengine.cc
+++ b/webrtc/media/engine/webrtcvoiceengine.cc
@@ -280,7 +280,11 @@ void GetOpusConfig(const AudioCodec& codec,
 webrtc::AudioState::Config MakeAudioStateConfig(VoEWrapper* voe_wrapper) {
   webrtc::AudioState::Config config;
   config.voice_engine = voe_wrapper->engine();
-  config.audio_mixer = webrtc::AudioMixerImpl::Create();
+  if (voe_wrapper->AudioMixer()) {

[the sun, 2016/12/07 15:56:08]

Send the mixer as an argument to this function instead of going via the
voe_wrapper

[GeorgeZ, 2016/12/07 18:28:17]

Good point

+    config.audio_mixer = voe_wrapper->AudioMixer();
+  } else {
+    config.audio_mixer = webrtc::AudioMixerImpl::Create();
+  }
   return config;
 }
 
@@ -540,14 +544,19 @@ bool WebRtcVoiceEngine::ToCodecInst(const AudioCodec& in,
 
 WebRtcVoiceEngine::WebRtcVoiceEngine(
     webrtc::AudioDeviceModule* adm,
-    const rtc::scoped_refptr<webrtc::AudioDecoderFactory>& decoder_factory)
-    : WebRtcVoiceEngine(adm, decoder_factory, new VoEWrapper()) {
+    const rtc::scoped_refptr<webrtc::AudioDecoderFactory>& decoder_factory,
+    rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer)
+    : WebRtcVoiceEngine(adm,
+                        decoder_factory,
+                        audio_mixer,
+                        new VoEWrapper(audio_mixer)) {
   audio_state_ = webrtc::AudioState::Create(MakeAudioStateConfig(voe()));
 }
 
 WebRtcVoiceEngine::WebRtcVoiceEngine(
     webrtc::AudioDeviceModule* adm,
     const rtc::scoped_refptr<webrtc::AudioDecoderFactory>& decoder_factory,
+    rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer,
     VoEWrapper* voe_wrapper)
     : adm_(adm), decoder_factory_(decoder_factory), voe_wrapper_(voe_wrapper) {
   RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());