fixes #168, dart:js implementation with a test

tool/input_sdk/patch/async_patch.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.
 
 // Patch file for the dart:async library.
 
 import 'dart:_js_helper' show
     patch,
-    Primitives,
-    convertDartClosureToJS;
+    Primitives;
 import 'dart:_isolate_helper' show
     IsolateNatives,
     TimerImpl,
     leaveJsAsync,
     enterJsAsync,
     isWorker;
 
 import 'dart:_foreign_helper' show JS;
 
 @patch
@@ skipping 18 matching lines @@
       var span = JS('', 'self.document.createElement("span")');
       var storedCallback;
 
       internalCallback(_) {
         leaveJsAsync();
         var f = storedCallback;
         storedCallback = null;
         f();
       };
 
-      var observer = JS('', 'new self.MutationObserver(#)',
-          convertDartClosureToJS(internalCallback, 1));
+      var observer = JS('', 'new self.MutationObserver(#)', internalCallback);
       JS('', '#.observe(#, { childList: true })',
           observer, div);
 
       return (void callback()) {
         assert(storedCallback == null);
         enterJsAsync();
         storedCallback = callback;
         // Because of a broken shadow-dom polyfill we have to change the
         // children instead a cheap property.
         // See https://github.com/Polymer/ShadowDOM/issues/468
         JS('', '#.firstChild ? #.removeChild(#): #.appendChild(#)',
             div, div, span, div, span);
       };
     } else if (JS('', 'self.setImmediate') != null) {
       return _scheduleImmediateWithSetImmediate;
     }
     // TODO(20055): We should use DOM promises when available.
     return _scheduleImmediateWithTimer;
   }
 
   static void _scheduleImmediateJsOverride(void callback()) {
     internalCallback() {
       leaveJsAsync();
       callback();
     };
     enterJsAsync();
-    JS('void', 'self.scheduleImmediate(#)',
-       convertDartClosureToJS(internalCallback, 0));
+    JS('void', 'self.scheduleImmediate(#)', internalCallback);
   }
 
   static void _scheduleImmediateWithSetImmediate(void callback()) {
     internalCallback() {
       leaveJsAsync();
       callback();
     };
     enterJsAsync();
-    JS('void', 'self.setImmediate(#)',
-       convertDartClosureToJS(internalCallback, 0));
+    JS('void', 'self.setImmediate(#)', internalCallback);
   }
 
   static void _scheduleImmediateWithTimer(void callback()) {
     Timer._createTimer(Duration.ZERO, callback);
   }
 }
 
 @patch
 class DeferredLibrary {
   @patch
@@ skipping 15 matching lines @@
   @patch
   static Timer _createPeriodicTimer(Duration duration,
                              void callback(Timer timer)) {
     int milliseconds = duration.inMilliseconds;
     if (milliseconds < 0) milliseconds = 0;
     return new TimerImpl.periodic(milliseconds, callback);
   }
 }
 
 bool get _hasDocument => JS('String', 'typeof document') == 'object';