Revert of 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 825e58025b4523a98b6770ddc75a75397a41c01f..e14b79ca6c45258e7b7b9a623b453d34fb3e7916 100644
--- a/webrtc/api/peerconnectioninterface.h
+++ b/webrtc/api/peerconnectioninterface.h
@@ -86,7 +86,6 @@
 
 namespace webrtc {
 class AudioDeviceModule;
-class AudioMixer;
 class MediaConstraintsInterface;
 
 // MediaStream container interface.
@@ -760,20 +759,6 @@
     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>