Introduce struct MediaConfig, with construction-time settings.

webrtc/pc/channelmanager.cc

Index: webrtc/pc/channelmanager.cc
diff --git a/webrtc/pc/channelmanager.cc b/webrtc/pc/channelmanager.cc
index ac2df8b0b8446df83e6321dd241ccc08b9840d69..dfa9c11f37d910d497857130072b10f88eab847f 100644
--- a/webrtc/pc/channelmanager.cc
+++ b/webrtc/pc/channelmanager.cc
@@ -267,8 +267,8 @@ VoiceChannel* ChannelManager::CreateVoiceChannel_w(
   ASSERT(initialized_);
   ASSERT(worker_thread_ == rtc::Thread::Current());
   ASSERT(nullptr != media_controller);
-  VoiceMediaChannel* media_channel =
-      media_engine_->CreateChannel(media_controller->call_w(), options);
+  VoiceMediaChannel* media_channel = media_engine_->CreateChannel(
+      media_controller->call_w(), media_controller->config(), options);
   if (!media_channel)
     return nullptr;
 
@@ -325,8 +325,8 @@ VideoChannel* ChannelManager::CreateVideoChannel_w(
   ASSERT(initialized_);
   ASSERT(worker_thread_ == rtc::Thread::Current());
   ASSERT(nullptr != media_controller);
-  VideoMediaChannel* media_channel =
-      media_engine_->CreateVideoChannel(media_controller->call_w(), options);
+  VideoMediaChannel* media_channel = media_engine_->CreateVideoChannel(
+      media_controller->call_w(), media_controller->config(), options);
   if (media_channel == NULL) {
     return NULL;
   }