Support asynchronuous spawnDomFunction.

tests/html/dom_isolates_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 DOMIsolatesTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 import 'dart:isolate';
 
 isolateMain() {
   port.receive((msg, replyTo) {
     if (msg != 'check') {
       replyTo.send('wrong msg: $msg');
     }
     replyTo.send('${window.location}');
     port.close();
   });
 }
 
 isolateMainTrampoline() {
-  final childPort = spawnDomFunction(isolateMain);
+  final future = spawnDomFunction(isolateMain);
   port.receive((msg, parentPort) {
-    childPort.call(msg).then((response) {
-      parentPort.send(response);
-      port.close();
+    future.then((childPort) {
+      childPort.call(msg).then((response) {
+        parentPort.send(response);
+        port.close();
+      });
     });
   });
 }
 
 dummy() => print("Bad invocation of top-level function");
 
 main() {
   useHtmlConfiguration();
 
   test('Simple DOM isolate test', () {
-    spawnDomFunction(isolateMain).call('check').then(
-      expectAsync1((msg) {
-        expect(msg, equals('${window.location}'));
-      }));
+    spawnDomFunction(isolateMain).then((sendPort) {
+      sendPort.call('check').then(
+        expectAsync1((msg) {
+          expect(msg, equals('${window.location}'));
+        }));
+    });
   });
 
   test('Nested DOM isolates test', () {
-    spawnDomFunction(isolateMainTrampoline).call('check').then(
-      expectAsync1((msg) {
-        expect(msg, equals('${window.location}'));
-      }));
+    spawnDomFunction(isolateMainTrampoline).then((sendPort) {
+      sendPort.call('check').then(
+        expectAsync1((msg) {
+          expect(msg, equals('${window.location}'));
+        }));
+    });
   });
 
   test('Not function', () {
       expect(() => spawnDomFunction(42), throws);
   });
 
   test('Not topLevelFunction', () {
     var closure = guardAsync(() {});
     expect(() => spawnDomFunction(closure), throws);
   });
 
   test('Masked local function', () {
     var local = 42;
     dummy() => print("Bad invocation of local function: $local");
     expect(() => spawnDomFunction(dummy), throws);
   });
 }