fixes #221, initial sync*, async, async* implementation

test/codegen/js_test.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.
 
 library jsTest;
 
 import 'dart:js';
 
 // TODO(jmesserly): get tests from package(s) instead.
 import 'dom.dart';
@@ skipping 685 matching lines @@
         context['o'] = ctx.createImageData(1, 1);
         var imageDataType = context['ImageData'];
         expect(context.callMethod('isPropertyInstanceOf', ['o', imageDataType]),
             true);
         context.deleteProperty('o');
       });
 
     });
   });
 }