Remove AsyncError with Expando.

tests/utils/dummy_compiler_test.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.
 
 // Smoke test of the dart2js compiler API.
 library dummy_compiler;
 
 import 'dart:async';
 import 'dart:uri';
 
@@ skipping 79 matching lines @@
 main() {
   Future<String> result =
       compile(new Uri.fromComponents(scheme: 'main'),
               new Uri.fromComponents(scheme: 'lib', path: '/'),
               new Uri.fromComponents(scheme: 'package', path: '/'),
               provider, handler);
   result.then((String code) {
     if (code == null) {
       throw 'Compilation failed';
     }
-  }, onError: (AsyncError e) {
+  }, onError: (e) {
       throw 'Compilation failed';
   });
 }