Allow p2p UDP packages to set DSCP

net/udp/udp_socket_libevent.h

Index: net/udp/udp_socket_libevent.h
diff --git a/net/udp/udp_socket_libevent.h b/net/udp/udp_socket_libevent.h
index 8f68a9b57a90695a87101eca856448198daedffb..30a788465f3f3b6e997c3cc2a856ba8360ef1860 100644
--- a/net/udp/udp_socket_libevent.h
+++ b/net/udp/udp_socket_libevent.h
@@ -21,7 +21,7 @@ namespace net {
 
 class NET_EXPORT UDPSocketLibevent : public base::NonThreadSafe {
  public:
-  UDPSocketLibevent(DatagramSocket::BindType bind_type,
+ UDPSocketLibevent(DatagramSocket::BindType bind_type,
                     const RandIntCallback& rand_int_cb,
                     net::NetLog* net_log,
                     const net::NetLog::Source& source);
@@ -151,6 +151,10 @@ class NET_EXPORT UDPSocketLibevent : public base::NonThreadSafe {
   // other applications on the same host. See MSDN: http://goo.gl/6vqbj
   int SetMulticastLoopbackMode(bool loopback);
 
+  // Set the differentiated services flags on outgoing packets. May not
+  // do anything on some platforms.
+  int SetToS(DiffServCodePoint dscp);
+
  private:
   static const int kInvalidSocket = -1;
 
@@ -237,6 +241,9 @@ class NET_EXPORT UDPSocketLibevent : public base::NonThreadSafe {
   // Cannot be used after Bind().
   int multicast_time_to_live_;
 
+  // Differentiated Services Code Point.
+  DiffServCodePoint dscp_;
+
   // How to do source port binding, used only when UDPSocket is part of
   // UDPClientSocket, since UDPServerSocket provides Bind.
   DatagramSocket::BindType bind_type_;