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

webrtc/pc/channelmanager.h

Index: webrtc/pc/channelmanager.h
diff --git a/webrtc/pc/channelmanager.h b/webrtc/pc/channelmanager.h
index 15a3752c44a730ae85ecaac07576825a990ffc8c..336c913406a2a9f62bdd3064426697493b33d308 100644
--- a/webrtc/pc/channelmanager.h
+++ b/webrtc/pc/channelmanager.h
@@ -108,11 +108,13 @@ class ChannelManager {
       const VideoOptions& options);
   // Destroys a video channel created with the Create API.
   void DestroyVideoChannel(VideoChannel* video_channel);
-  DataChannel* CreateDataChannel(TransportController* transport_controller,
-                                 const std::string& content_name,
-                                 const std::string* bundle_transport_name,
-                                 bool rtcp,
-                                 DataChannelType data_channel_type);
+  DataChannel* CreateDataChannel(
+      TransportController* transport_controller,
+      const std::string& content_name,
+      const std::string* bundle_transport_name,
+      bool rtcp,
+      DataChannelType data_channel_type,
+      webrtc::MediaControllerInterface* media_controller = nullptr);
   // Destroys a data channel created with the Create API.
   void DestroyDataChannel(DataChannel* data_channel);
 
@@ -171,11 +173,13 @@ class ChannelManager {
       bool rtcp,
       const VideoOptions& options);
   void DestroyVideoChannel_w(VideoChannel* video_channel);
-  DataChannel* CreateDataChannel_w(TransportController* transport_controller,
-                                   const std::string& content_name,
-                                   const std::string* bundle_transport_name,
-                                   bool rtcp,
-                                   DataChannelType data_channel_type);
+  DataChannel* CreateDataChannel_w(
+      TransportController* transport_controller,
+      const std::string& content_name,
+      const std::string* bundle_transport_name,
+      bool rtcp,
+      DataChannelType data_channel_type,
+      webrtc::MediaControllerInterface* media_controller);
   void DestroyDataChannel_w(DataChannel* data_channel);
 
   std::unique_ptr<MediaEngineInterface> media_engine_;