Add support of IP_MULTICAST_IF in UDP sockets.

net/udp/udp_socket_unittest.cc

Index: net/udp/udp_socket_unittest.cc
diff --git a/net/udp/udp_socket_unittest.cc b/net/udp/udp_socket_unittest.cc
index ffb56d98141d13700496894e65c526d086af33e0..20e38ee4c118f4e1c986789871e3ad4a7d682c42 100644
--- a/net/udp/udp_socket_unittest.cc
+++ b/net/udp/udp_socket_unittest.cc
@@ -574,9 +574,14 @@ TEST_F(UDPSocketTest, MulticastOptions) {
   EXPECT_EQ(OK, socket.SetMulticastTimeToLive(0));
   EXPECT_EQ(OK, socket.SetMulticastTimeToLive(3));
   EXPECT_NE(OK, socket.SetMulticastTimeToLive(-1));
+  EXPECT_EQ(OK, socket.SetMulticastInterface(0));
 
   EXPECT_EQ(OK, socket.Bind(bind_address));
 
+  EXPECT_NE(OK, socket.SetMulticastLoopbackMode(false));
+  EXPECT_NE(OK, socket.SetMulticastTimeToLive(0));
+  EXPECT_NE(OK, socket.SetMulticastInterface(0));
+
   socket.Close();
 }