Remove AsyncError with Expando.

tests/standalone/io/http_server_response_test.dart

 // Copyright (c) 2013, 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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 import "package:expect/expect.dart";
@@ skipping 15 matching lines @@
       .then((request) => request.close())
       .then((response) {
         int received = 0;
         response.listen(
             (data) => received += data.length,
             onDone: () {
               if (bytes != null) Expect.equals(received, bytes);
               client.close();
             },
             onError: (error) {
-              Expect.isTrue(error.error is HttpParserException);
+              Expect.isTrue(error is HttpParserException);
             });
       })
       .catchError((error) {
          client.close();
       }, test: (e) => e is HttpParserException);
   });
 }
 
 void testResponseDone() {
   testServerRequest((server, request) {
@@ skipping 117 matching lines @@
     }, test: (e) => e is HttpException);
   });
 }
 
 void main() {
   testResponseDone();
   testResponseAddStream();
   testBadResponseAdd();
   testBadResponseClose();
 }