Enable IPv6 by default 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}) {
     return _RawServerSocket.bind(address, port, backlog);
   }
@@ skipping 18 matching lines @@
 
   /* patch */ static InternetAddress get ANY_IP_V4 {
     return _InternetAddress.ANY_IP_V4;
   }
 
   /* patch */ static InternetAddress get ANY_IP_V6 {
     return _InternetAddress.ANY_IP_V6;
   }
 
   /* patch */ static Future<List<InternetAddress>> lookup(
-      String host, {InternetAddressType type: InternetAddressType.IP_V4}) {
+      String host, {InternetAddressType type: InternetAddressType.ANY}) {
     return _NativeSocket.lookup(host, type: type);
   }
 }
 
 class _InternetAddress implements InternetAddress {
   static const int _ADDRESS_LOOPBACK_IP_V4 = 0;
   static const int _ADDRESS_LOOPBACK_IP_V6 = 1;
   static const int _ADDRESS_ANY_IP_V4 = 2;
   static const int _ADDRESS_ANY_IP_V6 = 3;
 
@@ skipping 101 matching lines @@
   // Holds the port of the socket, null if not known.
   int localPort;
 
   // Holds the address used to connect or bind the socket.
   InternetAddress address;
 
   // Native port for socket services.
   static SendPort socketService;
 
   static Future<List<InternetAddress>> lookup(
-      String host, {InternetAddressType type: InternetAddressType.IP_V4}) {
+      String host, {InternetAddressType type: InternetAddressType.ANY}) {
     ensureSocketService();
     return socketService.call([HOST_NAME_LOOKUP, host, type._value])
         .then((response) {
           if (isErrorResponse(response)) {
             throw createError(response, "Failed host name lookup");
           } else {
             return response.skip(1).map((result) {
               var type = new InternetAddressType._from(result[0]);
               return new _InternetAddress(type, result[1], host, result[2]);
             }).toList();
@@ skipping 916 matching lines @@
     _raw.onBadCertificate = callback;
   }
 
   X509Certificate get peerCertificate {
     if (_raw == null) {
      throw new StateError("peerCertificate called on destroyed SecureSocket");
     }
     return _raw.peerCertificate;
   }
 }