convert isolates to use Future

runtime/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 ReceivePortFactory {
   factory ReceivePort() {
     return new ReceivePortImpl();
   }
 
   factory ReceivePort.singleShot() {
@@ skipping 117 matching lines @@
   // Forward the implementation of sending messages to the VM. Only port ids
   // are being handed to the VM.
   static _sendInternal(int sendId, int replyId, var message)
       native "SendPortImpl_sendInternal_";
 
   final int _id;
 }
 
 
 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>();
     SendPort port = _start(isolate, isLight);
-    result.complete(port);
-    return result;
+    completer.complete(port);
+    return completer.future;
   }
 
   // Starts a new isolate calling the run method on a new instance of the
   // remote class's type.
   // Returns the send port which is passed to the newly created isolate.
   // This method is being dispatched to from the public core library code.
   static SendPort _start(Isolate isolate, bool light)
       native "IsolateNatives_start";
 }