Mock up code completion.

dart/site/try/src/isolate_legacy.dart

 // Copyright (c) 2014, 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 trydart.isolate_legacy;
 
 import 'dart:isolate';
-import 'dart:async';
 
 ReceivePort spawnFunction(void function(SendPort port)) {
   ReceivePort port = new ReceivePort();
   Isolate.spawn(function, port.sendPort);
   return port;
 }
 
 ReceivePort spawnDomFunction(void function(SendPort port)) {
   throw 'spawnDomFunction is no more';
 }