Fix warnings in socket.dart.

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 745 matching lines @@
 }
 
 
 class SocketException implements IOException {
   final String message;
   final OSError osError;
   final InternetAddress address;
   final int port;
 
   const SocketException(this.message, {this.osError, this.address, this.port});
-  const SocketException.closed() : message = 'Socket has been closed';
+  const SocketException.closed()
+      : message = 'Socket has been closed',
+        osError = null,
+        address = null,
+        port = null;
 
   String toString() {
     StringBuffer sb = new StringBuffer();
     sb.write("SocketException");
     if (!message.isEmpty) {
       sb.write(": $message");
       if (osError != null) {
         sb.write(" ($osError)");
       }
     } else if (osError != null) {
       sb.write(": $osError");
     }
     if (address != null) {
       sb.write(", address = ${address.host}");
     }
     if (port != null) {
       sb.write(", port = $port");
     }
     return sb.toString();
   }
 }