Fix some analyzer warnings in dart:io.

sdk/lib/io/http.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;
 
 /**
  * HTTP status codes.
  */
 abstract class HttpStatus {
@@ skipping 1471 matching lines @@
 
 
 class RedirectException implements HttpException {
   final String message;
   final List<RedirectInfo> redirects;
 
   const RedirectException(String this.message,
                           List<RedirectInfo> this.redirects);
 
   String toString() => "RedirectException: $message";
+
+  Uri get uri => redirects.last.location;
 }