Add support of IP_MULTICAST_IF in UDP sockets.

net/udp/udp_socket_win.h

Index: net/udp/udp_socket_win.h
diff --git a/net/udp/udp_socket_win.h b/net/udp/udp_socket_win.h
index 142c692283e23c7c33f6066b2c3e62b1e7b27054..6f2877cb3f2c32faa10ecb5f2296ec4848cadbec 100644
--- a/net/udp/udp_socket_win.h
+++ b/net/udp/udp_socket_win.h
@@ -116,10 +116,10 @@ class NET_EXPORT UDPSocketWin : NON_EXPORTED_BASE(public base::NonThreadSafe) {
   void AllowBroadcast();
 
   // Join the multicast group.
-  // |group_address| is the group address to join, could be either
-  // an IPv4 or IPv6 address.
+  // |group_address| is the group address to join, could be either an IPv4 or
+  // IPv6 address.
   // Return a network error code.
-  int JoinGroup(const IPAddressNumber& group_address) const;
+  int JoinGroup(const IPAddressNumber& group_address);
 
   // Leave the multicast group.
   // |group_address| is the group address to leave, could be either
@@ -128,7 +128,11 @@ class NET_EXPORT UDPSocketWin : NON_EXPORTED_BASE(public base::NonThreadSafe) {
   // It's optional to leave the multicast group before destroying
   // the socket. It will be done by the OS.
   // Return a network error code.
-  int LeaveGroup(const IPAddressNumber& group_address) const;
+  int LeaveGroup(const IPAddressNumber& group_address);
+
+  // Set interface to listen and send multicast. If |interface_index| set to 0,
+  // default interface is used.
+  int SetMulticastInterface(uint32 interface_index);
 
   // Set the time-to-live option for UDP packets sent to the multicast
   // group address. The default value of this option is 1.
@@ -207,6 +211,9 @@ class NET_EXPORT UDPSocketWin : NON_EXPORTED_BASE(public base::NonThreadSafe) {
   // options that should be applied to |socket_| before Bind().
   int socket_options_;
 
+  // Multicast interface.
+  uint32 multicast_interface_;
+
   // Multicast socket options cached for SetSocketOption.
   // Cannot be used after Bind().
   int multicast_time_to_live_;