Remove AsyncError with Expando.

pkg/oauth2/test/authorization_code_grant_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.
 
 library authorization_code_grant_test;
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:json' as JSON;
 import 'dart:uri';
@@ skipping 15 matching lines @@
   client = new ExpectClient();
   grant = new oauth2.AuthorizationCodeGrant(
       'identifier',
       'secret',
       Uri.parse('https://example.com/authorization'),
       Uri.parse('https://example.com/token'),
       httpClient: client);
 }
 
 void expectFutureThrows(future, predicate) {
-  future.catchError(expectAsync1((AsyncError e) {
-    expect(predicate(e.error), isTrue);
+  future.catchError(expectAsync1((error) {
+    expect(predicate(error), isTrue);
   }));
 }
 
 void main() {
   group('.getAuthorizationUrl', () {
     setUp(createGrant);
 
     test('builds the correct URL', () {
       expect(grant.getAuthorizationUrl(redirectUrl).toString(),
           equals('https://example.com/authorization'
@@ skipping 157 matching lines @@
       });
 
       expect(grant.handleAuthorizationCode('auth code'),
           completion(predicate((client) {
             expect(client.credentials.accessToken, equals('access token'));
             return true;
           })));
     });
   });
 }