Remove AsyncError with Expando.

sdk/lib/io/websocket_impl.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.
 
 part of dart.io;
 
 const String _webSocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 
 class _WebSocketMessageType {
   static const int NONE = 0;
@@ skipping 546 matching lines @@
           _closeCode = WebSocketStatus.ABNORMAL_CLOSURE;
           _controller.addError(error);
           _controller.close();
         })
         .whenComplete(() {
           _writeClosed = true;
         });
   }
 
   StreamSubscription listen(void onData(message),
-                            {void onError(AsyncError error),
+                            {void onError(error),
                              void onDone(),
                              bool cancelOnError}) {
     return _controller.stream.listen(onData,
                                      onError: onError,
                                      onDone: onDone,
                                      cancelOnError: cancelOnError);
   }
 
   int get readyState => _readyState;
 
@@ skipping 109 matching lines @@
       if (data != null) {
         _socket.add(data);
       }
     } catch (_) {
       // The socket can be closed before _socket.done have a chance
       // to complete.
       _writeClosed = true;
     }
   }
 }