Adding HttpRequest method to make it easier to post form data.

tests/html/xhr_test.dart

 // 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.
 
 library XHRTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_individual_config.dart';
 import 'dart:async';
 import 'dart:html';
 import 'dart:json' as json;
@@ skipping 190 matching lines @@
         for (var i = 0; i < data.length; ++i) {
           data[i] = i & 0xFF;
         }
         xhr.send(data);
 
         return xhr.onLoad.first.then((_) {
           expect(progressCalled, isTrue);
         });
       });
     }
+
+    test('xhr postFormData', () {
+      var data = { 'name': 'John', 'time': '2 pm' };
+
+      var parts = [];
+      for (var key in data.keys) {
+        parts.add('${Uri.encodeQueryComponent(key)}='
+          '${Uri.encodeQueryComponent(data[key])}');
+      }
+      var encodedData = parts.join('&');
+
+      return HttpRequest.postFormData(
+          '${window.location.protocol}//${window.location.host}/echo', data)
+          .then((xhr) {
+          expect(xhr.responseText, encodedData);
+        });
+    });
+
   });
 
   group('xhr_requestBlob', () {
     test('XHR.request responseType blob', () {
       if (Platform.supportsTypedData) {
         return HttpRequest.request(url, responseType: 'blob').then(
           (xhr) {
             expect(xhr.status, equals(200));
             var blob = xhr.response;
             expect(blob is Blob, isTrue);
             expect(blob, isNotNull);
           });
       }
     });
   });
 }