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..bbfe789dd3b48a5abeb0540cd1551d00bdbfe69f 100644
--- a/webrtc/api/peerconnectioninterface.h
+++ b/webrtc/api/peerconnectioninterface.h
@@ -56,6 +56,7 @@
 #include <utility>
 #include <vector>
 
+#include "webrtc/api/audio/audio_mixer.h"
 #include "webrtc/api/datachannelinterface.h"
 #include "webrtc/api/dtmfsenderinterface.h"
 #include "webrtc/api/jsep.h"
@@ -535,6 +536,9 @@ class PeerConnectionInterface : public rtc::RefCountInterface {
   // Terminates all media and closes the transport.
   virtual void Close() = 0;
 
+  // Get remote audio tracks' ssrcs.
+  virtual std::vector<uint32_t> GetRemoteAudioTrackSsrcs() = 0;
+
  protected:
   // Dtor protected as objects shouldn't be deleted via this interface.
   ~PeerConnectionInterface() {}
@@ -773,6 +777,24 @@ CreatePeerConnectionFactory(
       default_adm, encoder_factory, decoder_factory);
 }
 
+// Create a new instance of PeerConnectionFactoryInterface with external audio
+// mixer.
+//
+// |network_thread|, |worker_thread| and |signaling_thread| are
+// the only mandatory parameters.
+//
+// If non-null, ownership of |default_adm|, |encoder_factory| and
+// |decoder_factory| are transferred to the returned factory.

[aleloi, 2016/12/05 14:03:08]

The comment should mention the new argument |audio_mixed|. For the other
arguments, I don't think the same thing has to be repeated as in the first
c-tor. (So only document the difference and the new parameter). Also, I think
this should be moved above the |worker_and_network_thread|-constructor, because
it's more similar to the first c-tor 

[GeorgeZ, 2016/12/05 17:56:18]

Done.

+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);
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_PEERCONNECTIONINTERFACE_H_