Add reverse dns lookup as a method on InternetAddress.

sdk/lib/io/socket.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.
 
 part of dart.io;
 
 
 /**
  * [InternetAddressType] is the type an [InternetAddress]. Currently,
  * IP version 4 (IPv4) and IP version 6 (IPv6) are supported.
@@ skipping 79 matching lines @@
    * Returns true if the [InternetAddress] is a loopback address.
    */
   bool get isLoopback;
 
   /**
    * Returns true if the [InternetAddress]s scope is a link-local.
    */
   bool get isLinkLocal;
 
   /**
+   * Perform a reverse dns lookup on the [address], creating a new
+   * [InternetAddress] where the host field set to the result.
+   */
+  Future<InternetAddress> reverse();
+
+  /**
    * Lookup a host, returning a Future of a list of
    * [InternetAddress]s. If [type] is [InternetAddressType.ANY], it
    * will lookup both IP version 4 (IPv4) and IP version 6 (IPv6)
    * addresses. If [type] is either [InternetAddressType.IP_V4] or
    * [InternetAddressType.IP_V6] it will only lookup addresses of the
    * specified type. The order of the list can, and most likely will,
    * change over time.
    */
   external static Future<List<InternetAddress>> lookup(
       String host, {InternetAddressType type: InternetAddressType.ANY});
@@ skipping 359 matching lines @@
         sb.write(" ($osError)");
       }
     } else if (osError != null) {
       sb.write(": $osError");
     }
     return sb.toString();
   }
   final String message;
   final OSError osError;
 }