Create generated tests inside the build directory

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:html';
 import 'dart:json' as json;
 
 void fail(message) {
   guardAsync(() {
     expect(false, isTrue, reason: message);
   });
 }
 
 main() {
   useHtmlIndividualConfiguration();
-  var url = "/tests/html/xhr_cross_origin_data.txt";
+  var url = "/root_dart/tests/html/xhr_cross_origin_data.txt";
 
   void validate200Response(xhr) {
     expect(xhr.status, equals(200));
     var data = json.parse(xhr.response);
     expect(data, contains('feed'));
     expect(data['feed'], contains('entry'));
     expect(data, isMap);
   }
 
   void validate404(xhr) {
@@ skipping 109 matching lines @@
     test('HttpRequestProgressEvent', () {
       var expectation = HttpRequestProgressEvent.supported ?
           returnsNormally : throws;
       expect(() {
         var event = new Event.eventType('XMLHttpRequestProgressEvent', '');
         expect(event is HttpRequestProgressEvent, isTrue);
       }, expectation);
     });
   });
 }