[dart:io] Ignore server http upgrade request unless status code is right

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 25 matching lines @@
   static const int REQUEST_TIMEOUT = 408;
   static const int CONFLICT = 409;
   static const int GONE = 410;
   static const int LENGTH_REQUIRED = 411;
   static const int PRECONDITION_FAILED = 412;
   static const int REQUEST_ENTITY_TOO_LARGE = 413;
   static const int REQUEST_URI_TOO_LONG = 414;
   static const int UNSUPPORTED_MEDIA_TYPE = 415;
   static const int REQUESTED_RANGE_NOT_SATISFIABLE = 416;
   static const int EXPECTATION_FAILED = 417;
+  static const int UPGRADE_REQUIRED = 426;
   static const int INTERNAL_SERVER_ERROR = 500;
   static const int NOT_IMPLEMENTED = 501;
   static const int BAD_GATEWAY = 502;
   static const int SERVICE_UNAVAILABLE = 503;
   static const int GATEWAY_TIMEOUT = 504;
   static const int HTTP_VERSION_NOT_SUPPORTED = 505;
   // Client generated status code.
   static const int NETWORK_CONNECT_TIMEOUT_ERROR = 599;
 }
 
@@ skipping 1939 matching lines @@
 class RedirectException implements HttpException {
   final String message;
   final List<RedirectInfo> redirects;
 
   const RedirectException(this.message, this.redirects);
 
   String toString() => "RedirectException: $message";
 
   Uri get uri => redirects.last.location;
 }