convert isolates to use Future

frog/lib/isolate.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.
 
 class SendPortImpl implements SendPort {
 
   const SendPortImpl(this._workerId, this._isolateId, this._receivePortId);
 
   void send(var message, [SendPort replyTo = null]) {
     // TODO(kasperl): get rid of _sendNow.
@@ skipping 135 matching lines @@
     return _port._toNewSendPort();
   }
 
   final ReceivePortImpl _port;
 
 }
 
 final String _SPAWNED_SIGNAL = "spawned";
 
 class IsolateNatives {
-  static Promise<SendPort> spawn(Isolate isolate, bool isLight) {
-    Promise<SendPort> result = new Promise<SendPort>();
+  static Future<SendPort> spawn(Isolate isolate, bool isLight) {
+    Completer<SendPort> completer = new Completer<SendPort>();
     ReceivePort port = new ReceivePort.singleShot();
     port.receive((msg, SendPort replyPort) {
       assert(msg == _SPAWNED_SIGNAL);
-      result.complete(replyPort);
+      completer.complete(replyPort);
     });
     _spawn(isolate, isLight, port.toSendPort());
-    return result;
+    return completer.future;
   }
 
   static SendPort _spawn(Isolate isolate, bool light, SendPort port) native;
   static Function bind(Function f) native;
 }
 
 
 class _IsolateJsUtil {
   static void _startIsolate(Isolate isolate, SendPort replyTo) native {
     ReceivePort port = new ReceivePort();
@@ skipping 14 matching lines @@
   }
 
   static _serializeObject(obj) native {
     return new Serializer().traverse(obj);
   }
 
   static _deserializeMessage(message) native {
     return new Deserializer().deserialize(message);
   }
 }