Implement spawnDomFunction

lib/dom/src/native_DOMPublic.dart

 // Copyright (c) 2011, 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.
 
 // This API is exploratory.
-spawnDomIsolate(Window targetWindow, String entryPoint) {
-  if (targetWindow is! _DOMWindowImpl && targetWindow is! _DOMWindowCrossFrameImpl) {
-    throw 'Bad window argument: $targetWindow';
-  }
-  final result = new Completer<SendPort>();
-  final port = _Utils.spawnDomIsolateImpl(targetWindow, entryPoint);
-  window.setTimeout(() { result.complete(port); }, 0);
-  return result.future;
+spawnDomFunction(Function topLevelFunction) {
+  return _Utils.spawnDomFunctionImpl(topLevelFunction);
 }
 
 // layoutTestController implementation.
 // FIXME: provide a separate lib for layoutTestController.
 
 var _layoutTestController;
 
 LayoutTestController get layoutTestController() {
   if (_layoutTestController === null)
     _layoutTestController = new LayoutTestController._(_NPObject.retrieve("layoutTestController"));
   return _layoutTestController;
 }
 
 class LayoutTestController {
   final _NPObject _npObject;
 
   LayoutTestController._(this._npObject);
 
   display() => _npObject.invoke('display');
   dumpAsText() => _npObject.invoke('dumpAsText');
   notifyDone() => _npObject.invoke('notifyDone');
   setCanOpenWindows() => _npObject.invoke('setCanOpenWindows');
   waitUntilDone() => _npObject.invoke('waitUntilDone');
 }