Remove the reply port form the native isolate handler

samples/sample_extension/sample_asynchronous_extension.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 sample_asynchronous_extension;
 
 import 'dart:async';
 import 'dart:isolate';
 import 'dart-ext:sample_extension';
 
 // A class caches the native port used to call an asynchronous extension.
 class RandomArray {
   static SendPort _port;
 
-  Future<List<int>> randomArray(int seed, int length) {
-    var args = new List(2);
+  Future<List<int> > randomArray(int seed, int length) {
+    var completer = new Completer();
+    var replyPort = new RawReceivePort();
+    var args = new List(3);
     args[0] = seed;
     args[1] = length;
-    ReceivePort receivePort = new ReceivePort();
-    _servicePort.send(args, receivePort.sendPort);
-    return receivePort.first.then((result) {
-      receivePort.close();
+    args[2] = replyPort.sendPort;
+    _servicePort.send(args);
+    replyPort.handler = (result) {
+      replyPort.close();
       if (result != null) {
-        return result;
+        completer.complete(result);
       } else {
-        throw new Exception("Random array creation failed");
+        completer.completeError(new Exception("Random array creation failed"));
       }
-    });
+    };
+    return completer.future;
   }
 
   SendPort get _servicePort {
     if (_port == null) {
       _port = _newServicePort();
     }
     return _port;
   }
 
   SendPort _newServicePort() native "RandomArray_ServicePort";
 }