Add new InternetAddress class with a static lookup function (including IPv6 results).

sdk/lib/io/socket.dart

Index: sdk/lib/io/socket.dart
diff --git a/sdk/lib/io/socket.dart b/sdk/lib/io/socket.dart
index c5eb054109a2b59d1b5934847f4952608748e944..88cbd08f7f16416a415f2877ea89316ea9eec22d 100644
--- a/sdk/lib/io/socket.dart
+++ b/sdk/lib/io/socket.dart
@@ -4,6 +4,37 @@
 
 part of dart.io;
 
+
+class InternetAddressType {
+  static const InternetAddressType IPv4 = const InternetAddressType._(0);
+  static const InternetAddressType IPv6 = const InternetAddressType._(1);
+
+  final int _value;
+
+  const InternetAddressType._(String this._value);
+
+  String get name {
+    switch (_value) {
+      case 0: return "IPv4";
+      case 1: return "IPv6";
+      default: throw new ArgumentError("Invalid InternetAddress");
+    }
+  }
+
+  String toString() => "InternetAddressType($name)";
+
+  int get hashCode => _value;
+
+  bool operator==(other) => _value == other._value;
+}
+
+abstract class InternetAddress {
+  InternetAddressType type;
+  String get address;
+
+  external static Future<List<InternetAddress>> lookup(String host);
+}
+
 /**
  * The RawServerSocket is a server socket, providing a stream of low-level
  * [RawSocket]s.
@@ -144,8 +175,12 @@ abstract class RawSocket implements Stream<RawSocketEvent> {
    * Creates a new socket connection to the host and port and returns a [Future]
    * that will complete with either a [RawSocket] once connected or an error
    * if the host-lookup or connection failed.
+   *
+   * [host] can either be a [String] or an [InternetAddress]. If [host] is a
+   * [String], [connect] will perform a [InternetAddress.lookup] and use
+   * the first value in the list.
    */
-  external static Future<RawSocket> connect(String host, int port);
+  external static Future<RawSocket> connect(host, int port);
 
   /**
    * Returns the number of received and non-read bytes in the socket that
@@ -233,8 +268,12 @@ abstract class Socket implements Stream<List<int>>, IOSink {
    * Creats a new socket connection to the host and port and returns a [Future]
    * that will complete with either a [Socket] once connected or an error
    * if the host-lookup or connection failed.
+   *
+   * [host] can either be a [String] or an [InternetAddress]. If [host] is a
+   * [String], [connect] will perform a [InternetAddress.lookup] and use
+   * the first value in the list.
    */
-  external static Future<Socket> connect(String host, int port);
+  external static Future<Socket> connect(host, int port);
 
   /**
    * Destroy the socket in both directions. Calling [destroy] will make the