Introduce struct MediaConfig, with construction-time settings.

webrtc/api/peerconnectionfactory.cc

Index: webrtc/api/peerconnectionfactory.cc
diff --git a/webrtc/api/peerconnectionfactory.cc b/webrtc/api/peerconnectionfactory.cc
index c3dec666f53a23aefe31a34b18ab8ef5e01a74d8..c05cd852f605faada5dbd47e68e7b2ec8afd94e8 100644
--- a/webrtc/api/peerconnectionfactory.cc
+++ b/webrtc/api/peerconnectionfactory.cc
@@ -286,10 +286,10 @@ PeerConnectionFactory::CreateAudioTrack(const std::string& id,
   return AudioTrackProxy::Create(signaling_thread_, track);
 }
 
-webrtc::MediaControllerInterface* PeerConnectionFactory::CreateMediaController()
-    const {
+webrtc::MediaControllerInterface* PeerConnectionFactory::CreateMediaController(
+    const cricket::MediaConfig& config) const {
   RTC_DCHECK(signaling_thread_->IsCurrent());
-  return MediaControllerInterface::Create(worker_thread_,
+  return MediaControllerInterface::Create(config, worker_thread_,
                                           channel_manager_.get());
 }