Fixing custom event test on IE

tests/html/event_customevent_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 EventCustomEventTest;
 
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
+import 'dart:js' as js;
 
 class DartPayloadData {
   final dartValue;
 
   DartPayloadData(this.dartValue);
 }
 
 main() {
   useHtmlConfiguration();
 
@@ skipping 27 matching lines @@
     });
 
     var script = new ScriptElement();
     script.text = scriptContents;
     document.body.append(script);
 
     expect(fired, isTrue);
   });
 
   test('custom events to JS', () {
+    expect(js.context['gotDartEvent'], isNull);
     var scriptContents = '''
       window.addEventListener('dart_custom_event', function(e) {
         if (e.detail == 'dart_message') {
           e.preventDefault();
+          window.gotDartEvent = true;
         }
+        window.console.log('here' + e.detail);

[vsm, 2013/10/16 23:49:01]

Do we need this print?

[blois, 2013/10/17 00:05:32]

Nope, gone.

       }, false);''';
 
     document.body.append(new ScriptElement()..text = scriptContents);
 
     var event = new CustomEvent('dart_custom_event', detail: 'dart_message');
     window.dispatchEvent(event);
-    expect(event.defaultPrevented, isTrue);
+    expect(js.context['gotDartEvent'], isTrue);
   });
 
   test('custom data to Dart', () {
     var data = new DartPayloadData(666);
     var event = new CustomEvent('dart_custom_data_event', detail: data);
 
     var future = window.on['dart_custom_data_event'].first.then((_) {
       expect(event.detail.dartValue, 666);
     });
 
     document.body.dispatchEvent(event);
     return future;
   });
 }