Cast: Use DSCP AF41 for all traffic if possible.

media/cast/transport/cast_transport_sender_impl.cc

Index: media/cast/transport/cast_transport_sender_impl.cc
diff --git a/media/cast/transport/cast_transport_sender_impl.cc b/media/cast/transport/cast_transport_sender_impl.cc
index 2f51a934e7d60bdea157946e659d3736007db8d6..c440c6c1b8380f06cd4ff0cb830a318ca1e614b4 100644
--- a/media/cast/transport/cast_transport_sender_impl.cc
+++ b/media/cast/transport/cast_transport_sender_impl.cc
@@ -7,6 +7,7 @@
 #include "base/single_thread_task_runner.h"
 #include "media/cast/transport/cast_transport_config.h"
 #include "media/cast/transport/cast_transport_defines.h"
+#include "net/base/net_util.h"
 
 namespace media {
 namespace cast {
@@ -66,6 +67,11 @@ CastTransportSenderImpl::CastTransportSenderImpl(
                             this,
                             &CastTransportSenderImpl::SendRawEvents);
   }
+  if (transport_) {
+    // The default DSCP value for cast is AF41. Which gives it a higher
+    // priority over other traffic.
+    transport_->SetDscp(net::DSCP_AF41);
+  }
 }
 
 CastTransportSenderImpl::~CastTransportSenderImpl() {