Add NetworkUtil function for marking sockets

Add NetworkUtil function for setting the SO_MARK field of sockets

Change-Id: I94389b64296d87ee928293f24a26f8dd08c3bf37

core/java/android/net/NetworkUtils.java

@@ -103,6 +103,11 @@ public class NetworkUtils {
      */
     public native static String getDhcpError();
 
+    /**
+     * Set the SO_MARK of {@code socketfd} to {@code mark}
+     */
+    public native static void markSocket(int socketfd, int mark);
+
     /**
      * Convert a IPv4 address from an integer to an InetAddress.
      * @param hostAddress an int corresponding to the IPv4 address in network byte order