Don't decodeHttpEntityString on urlencoded post data.

sdk/lib/io/http_body_impl.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;
 
 class _HttpBodyHandlerTransformer
     extends StreamEventTransformer<HttpRequest, HttpRequestBody> {
   final Encoding _defaultEncoding;
   _HttpBodyHandlerTransformer(this._defaultEncoding);
@@ skipping 105 matching lines @@
                 .then((body) => new _HttpBody(contentType,
                                               "json",
                                               JSON.parse(body.body)));
 
           case "x-www-form-urlencoded":
             return asText(Encoding.ASCII)
                 .then((body) {
                   var map = _HttpUtils.splitQueryString(
                       body.body, encoding: defaultEncoding);
                   var result = {};
-                  String parse(String s) {
-                    return _HttpUtils.decodeHttpEntityString(s);
-                  }
                   for (var key in map.keys) {
-                    result[parse(key)] = parse(map[key]);
+                    result[key] = map[key];
                   }
                   return new _HttpBody(contentType, "form", result);
                 });
 
           default:
             break;
         }
         break;
 
       case "multipart":
@@ skipping 52 matching lines @@
   _HttpClientResponseBody(HttpClientResponse response, HttpBody body)
       : super(body.contentType, body.type, body.body),
         this.response = response;
 
   int get statusCode => response.statusCode;
 
   String get reasonPhrase => response.reasonPhrase;
 
   HttpHeaders get headers => response.headers;
 }