Support external audio mixer.

webrtc/api/peerconnectioninterface.h

Index: webrtc/api/peerconnectioninterface.h
diff --git a/webrtc/api/peerconnectioninterface.h b/webrtc/api/peerconnectioninterface.h
index e14b79ca6c45258e7b7b9a623b453d34fb3e7916..825e58025b4523a98b6770ddc75a75397a41c01f 100644
--- a/webrtc/api/peerconnectioninterface.h
+++ b/webrtc/api/peerconnectioninterface.h
@@ -86,6 +86,7 @@ class WebRtcVideoEncoderFactory;
 
 namespace webrtc {
 class AudioDeviceModule;
+class AudioMixer;
 class MediaConstraintsInterface;
 
 // MediaStream container interface.
@@ -759,6 +760,20 @@ rtc::scoped_refptr<PeerConnectionFactoryInterface> CreatePeerConnectionFactory(
     cricket::WebRtcVideoEncoderFactory* encoder_factory,
     cricket::WebRtcVideoDecoderFactory* decoder_factory);
 
+// Create a new instance of PeerConnectionFactoryInterface with external audio
+// mixer.
+//
+// If |audio_mixer| is null, an internal audio mixer will be created and used.
+rtc::scoped_refptr<PeerConnectionFactoryInterface>
+CreatePeerConnectionFactoryWithAudioMixer(
+    rtc::Thread* network_thread,
+    rtc::Thread* worker_thread,
+    rtc::Thread* signaling_thread,
+    AudioDeviceModule* default_adm,
+    cricket::WebRtcVideoEncoderFactory* encoder_factory,
+    cricket::WebRtcVideoDecoderFactory* decoder_factory,
+    rtc::scoped_refptr<AudioMixer> audio_mixer);
+
 // Create a new instance of PeerConnectionFactoryInterface.
 // Same thread is used as worker and network thread.
 inline rtc::scoped_refptr<PeerConnectionFactoryInterface>