Remove AsyncError with Expando.

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:async";
 import "dart:io";
 
 import "test_suite.dart";
@@ skipping 12 matching lines @@
   _DartiumUpdater(this.name, this.script, [this.option = null]);
 
   void update() {
     if (!isActive) {
       isActive = true;
       print('Updating $name.');
       onUpdated = [() {updated = true;} ];
       _updatingProcess = Process.run('python', _getUpdateCommand);
       _updatingProcess.then(_onUpdatedHandler).catchError((e) {
         print("Error starting $script process: $e");
+        // TODO(floitsch): should we print the stacktrace?
         return false;
       });
     }
   }
 
   List<String> get _getUpdateCommand {
     Path testScriptPath = new Path(TestUtils.testScriptPath);
     Path updateScriptPath = testScriptPath.directoryPath.append(script);
     List<String> command = [updateScriptPath.toNativePath()];
     if (null != option) {
@@ skipping 32 matching lines @@
     // Download the default Dartium from Google Storage.
     if (_dartiumUpdater == null) {
       _dartiumUpdater = new _DartiumUpdater('Dartium Chrome', 'get_archive.py',
                                             'dartium');
     }
     return _dartiumUpdater;
   } else {
     return null;
   }
 }