Fixing dartium xhr issue

tools/dom/templates/html/impl/impl_XMLHttpRequest.darttemplate

 // Copyright (c) 2012, 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 $LIBRARYNAME;
 
 /**
  * A utility for retrieving data from a URL.
  *
  * HttpRequest can be used to obtain data from http, ftp, and file
@@ skipping 56 matching lines @@
    * * Using credentials is only useful for cross-origin requests.
    * * The `Access-Control-Allow-Origin` header of `url` cannot contain a wildcard (*).
    * * The `Access-Control-Allow-Credentials` header of `url` must be set to true.
    * * If `Access-Control-Expose-Headers` has not been set to true, only a subset of all the response headers will be returned when calling [getAllRequestHeaders].
    *
    * See also: [authorization headers](http://en.wikipedia.org/wiki/Basic_access_authentication).
    */
   static Future<HttpRequest> request(String url,
       {String method, bool withCredentials, String responseType, sendData,
       void onProgress(ProgressEvent e)}) {
-    var completer = new Completer<String>();
+    var completer = new Completer<HttpRequest>();
 
     var xhr = new HttpRequest();
     if (method == null) {
       method = 'GET';
     }
     xhr.open(method, url, true);
 
     if (withCredentials != null) {
       xhr.withCredentials = withCredentials;
     }
@@ skipping 23 matching lines @@
       xhr.send(sendData);
     } else {
       xhr.send();
     }
 
     return completer.future;
   }
 
 $!MEMBERS
 }