Support external audio mixer.

webrtc/media/engine/webrtcmediaengine.cc

Index: webrtc/media/engine/webrtcmediaengine.cc
diff --git a/webrtc/media/engine/webrtcmediaengine.cc b/webrtc/media/engine/webrtcmediaengine.cc
index 51a110b88b645aa2678991a9abede312f34463b7..34119088d4c181312311e557a9814e350130769f 100644
--- a/webrtc/media/engine/webrtcmediaengine.cc
+++ b/webrtc/media/engine/webrtcmediaengine.cc
@@ -33,13 +33,18 @@ class WebRtcMediaEngine2
                      const rtc::scoped_refptr<webrtc::AudioDecoderFactory>&
                          audio_decoder_factory,
                      WebRtcVideoEncoderFactory* video_encoder_factory,
-                     WebRtcVideoDecoderFactory* video_decoder_factory)
+                     WebRtcVideoDecoderFactory* video_decoder_factory,
+                     rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer)
 #ifdef HAVE_WEBRTC_VIDEO
       : CompositeMediaEngine<WebRtcVoiceEngine, WebRtcVideoEngine2>(
-            adm, audio_decoder_factory){
+            adm,
+            audio_decoder_factory,
+            audio_mixer){
 #else
       : CompositeMediaEngine<WebRtcVoiceEngine, NullWebRtcVideoEngine>(
-            adm, audio_decoder_factory) {
+            adm,
+            audio_decoder_factory,
+            audio_mixer) {
 #endif
     video_.SetExternalDecoderFactory(video_decoder_factory);
     video_.SetExternalEncoderFactory(video_encoder_factory);
@@ -53,9 +58,11 @@ cricket::MediaEngineInterface* CreateWebRtcMediaEngine(
     const rtc::scoped_refptr<webrtc::AudioDecoderFactory>&
         audio_decoder_factory,
     cricket::WebRtcVideoEncoderFactory* video_encoder_factory,
-    cricket::WebRtcVideoDecoderFactory* video_decoder_factory) {
-  return new cricket::WebRtcMediaEngine2(
-      adm, audio_decoder_factory, video_encoder_factory, video_decoder_factory);
+    cricket::WebRtcVideoDecoderFactory* video_decoder_factory,
+    rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer) {
+  return new cricket::WebRtcMediaEngine2(adm, audio_decoder_factory,
+                                         video_encoder_factory,
+                                         video_decoder_factory, audio_mixer);
 }
 
 void DestroyWebRtcMediaEngine(cricket::MediaEngineInterface* media_engine) {
@@ -70,10 +77,11 @@ namespace cricket {
 MediaEngineInterface* WebRtcMediaEngineFactory::Create(
     webrtc::AudioDeviceModule* adm,
     WebRtcVideoEncoderFactory* video_encoder_factory,
-    WebRtcVideoDecoderFactory* video_decoder_factory) {
-  return CreateWebRtcMediaEngine(adm,
-                                 webrtc::CreateBuiltinAudioDecoderFactory(),
-                                 video_encoder_factory, video_decoder_factory);
+    WebRtcVideoDecoderFactory* video_decoder_factory,
+    rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer) {

[the sun, 2016/12/12 20:50:04]

Again, breaking compatibility in this function is probably going to make life
harder for you, so only change the one called from PeerConnectionFactory.

+  return CreateWebRtcMediaEngine(
+      adm, webrtc::CreateBuiltinAudioDecoderFactory(), video_encoder_factory,
+      video_decoder_factory, audio_mixer);
 }
 
 // Used by PeerConnectionFactory to create a media engine passed into
@@ -83,9 +91,11 @@ MediaEngineInterface* WebRtcMediaEngineFactory::Create(
     const rtc::scoped_refptr<webrtc::AudioDecoderFactory>&
         audio_decoder_factory,
     WebRtcVideoEncoderFactory* video_encoder_factory,
-    WebRtcVideoDecoderFactory* video_decoder_factory) {
+    WebRtcVideoDecoderFactory* video_decoder_factory,
+    rtc::scoped_refptr<webrtc::AudioMixer> audio_mixer) {
   return CreateWebRtcMediaEngine(adm, audio_decoder_factory,
-                                 video_encoder_factory, video_decoder_factory);
+                                 video_encoder_factory, video_decoder_factory,
+                                 audio_mixer);
 }
 
 namespace {