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

webrtc/pc/channelmanager.cc

Index: webrtc/pc/channelmanager.cc
diff --git a/webrtc/pc/channelmanager.cc b/webrtc/pc/channelmanager.cc
index 255730a0ba4a9da381337c4c589b7f682b06205b..385084ccceb3514ce07103d3731e27befd7e7792 100644
--- a/webrtc/pc/channelmanager.cc
+++ b/webrtc/pc/channelmanager.cc
@@ -345,11 +345,13 @@ DataChannel* ChannelManager::CreateDataChannel(
     const std::string& content_name,
     const std::string* bundle_transport_name,
     bool rtcp,
-    DataChannelType channel_type) {
+    DataChannelType channel_type,
+    webrtc::MediaControllerInterface* media_controller) {
   return worker_thread_->Invoke<DataChannel*>(
       RTC_FROM_HERE,
       Bind(&ChannelManager::CreateDataChannel_w, this, transport_controller,
-           content_name, bundle_transport_name, rtcp, channel_type));
+           content_name, bundle_transport_name, rtcp, channel_type,
+           media_controller));
 }
 
 DataChannel* ChannelManager::CreateDataChannel_w(
@@ -357,11 +359,12 @@ DataChannel* ChannelManager::CreateDataChannel_w(
     const std::string& content_name,
     const std::string* bundle_transport_name,
     bool rtcp,
-    DataChannelType data_channel_type) {
+    DataChannelType data_channel_type,
+    webrtc::MediaControllerInterface* media_controller) {
   // This is ok to alloc from a thread other than the worker thread.
   ASSERT(initialized_);
   DataMediaChannel* media_channel = data_media_engine_->CreateChannel(
-      data_channel_type);
+      data_channel_type, media_controller->config());
   if (!media_channel) {
     LOG(LS_WARNING) << "Failed to create data channel of type "
                     << data_channel_type;