Change dart:io to use Future for one-shot operations.

tools/testing/dart/drt_updater.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("drt_updater");
 
 #import("dart:io");
 #import("dart:builtin");
 
 class _DartiumUpdater {
   String name;
   String script;
   String option;
 
   bool isActive = false;
   bool updated = false;
   List onUpdated;
 
-  Process _updatingProcess;
+  InteractiveProcess _updatingProcess;
 
   _DartiumUpdater(this.name, this.script, [this.option = null]);
 
   void update() {
     if (!isActive) {
       isActive = true;
       print('Updating $name.');
       onUpdated = [() {updated = true;} ];
-      _updatingProcess = new Process.start('python', _getUpdateCommand);
+      _updatingProcess = Process.start('python', _getUpdateCommand);
       _updatingProcess.onExit = _onUpdatedHandler;
       _updatingProcess.onError = (error) {
         print("Error starting $script process: $error");
         _onUpdatedHandler(-1);  // Continue anyway.
       };
     }
   }
 
   List<String> get _getUpdateCommand() {
     String scriptPath = new Options().script.replaceAll('\\', '/');
@@ skipping 27 matching lines @@
     // Download the default Dartium from Google Storage.
     if (_dartiumUpdater === null) {
       _dartiumUpdater = new _DartiumUpdater('Dartium Chrome', 'get_drt.py',
                                             '--dartium');
     }
     return _dartiumUpdater;
   } else {
     return null;
   }
 }