Implement spawnDomFunction

tests/html/js_interop_4_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('JsInterop4Test');
 #import('../../lib/unittest/unittest.dart');
 #import('../../lib/unittest/html_config.dart');
 #import('dart:html');
 #import('dart:isolate');
 
@@ skipping 41 matching lines @@
     var done = expectAsync0(() {});
     var fun2 = (message) {
       Expect.equals(3, message);
       window.setTimeout(done, 0);
     };
 
     var port2 = new ReceivePortSync();
     port2.receive(fun2);
     window.registerPort('fun2', port2.toSendPort());
 
-    spawnFunction(testIsolateEntry);
+    spawnDomFunction(testIsolateEntry);
   });
 }