Fix strong mode errors in dart:io.

runtime/bin/socket_patch.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 patch class RawServerSocket {
   /* patch */ static Future<RawServerSocket> bind(address,
                                                   int port,
                                                   {int backlog: 0,
                                                    bool v6Only: false,
                                                    bool shared: false}) {
@@ skipping 28 matching lines @@
   }
 
   /* patch */ factory InternetAddress(String address) {
     return new _InternetAddress.parse(address);
   }
 
   /* patch */ static Future<List<InternetAddress>> lookup(
       String host, {InternetAddressType type: InternetAddressType.ANY}) {
     return _NativeSocket.lookup(host, type: type);
   }
+
+  /* patch */ static InternetAddress _cloneWithNewHost(
+      InternetAddress address, String host) {
+    return (address as _InternetAddress)._cloneWithNewHost(host);
+  }
 }
 
 patch class NetworkInterface {
   /* patch */ static bool get listSupported {
     return _listSupported();
   }
 
   /* patch */ static Future<List<NetworkInterface>> list({
       bool includeLoopback: false,
       bool includeLinkLocal: false,
@@ skipping 1793 matching lines @@
 Datagram _makeDatagram(List<int> data,
                        String address,
                        List<int> in_addr,
                        int port) {
   return new Datagram(
       data,
       new _InternetAddress(address, null, in_addr),
       port);
 }