Set the preferred DSCP value for Rtp data channel to be DSCP_AF41.

webrtc/api/webrtcsession.cc

Index: webrtc/api/webrtcsession.cc
diff --git a/webrtc/api/webrtcsession.cc b/webrtc/api/webrtcsession.cc
index ded3023653247f827c2db0b6fa47f40a1a498aee..b893e1937acc42d1deb9d704f57af258ee9c9340 100644
--- a/webrtc/api/webrtcsession.cc
+++ b/webrtc/api/webrtcsession.cc
@@ -1720,7 +1720,7 @@ bool WebRtcSession::CreateDataChannel(const cricket::ContentInfo* content,
   bool create_rtcp_transport_channel = !sctp && !require_rtcp_mux;
   data_channel_.reset(channel_manager_->CreateDataChannel(
       transport_controller_.get(), content->name, bundle_transport,
-      create_rtcp_transport_channel, data_channel_type_));
+      create_rtcp_transport_channel, data_channel_type_, media_controller_));

[pthatcher1, 2016/12/06 00:06:01]

This should be after transport_controller_.get() but before content->name.

   if (!data_channel_) {
     return false;
   }