Make sure to process WebSocket frames when closing a WebSocket

tests/standalone/io/web_socket_pipe_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 22 matching lines @@
     WebSocket.connect("ws://127.0.0.1:${server.port}/").then((client) {
       var count = 0;
       next() {
         if (count < messages) {
           client.add("Hello");
         } else {
           client.close();
         }
       }
 
-      next();
       client.listen(
           (data) {
             count++;
             if (transform) {
               Expect.equals("olleH", data);
             } else {
               Expect.equals("Hello", data);
             }
             next();
           },
           onDone: () => print("Client received close"));
+
+      next();
     });
   });
 }
 
 void main() {
   testPipe(messages: 0, transform: false);
   testPipe(messages: 0, transform: true);
   testPipe(messages: 1, transform: false);
   testPipe(messages: 1, transform: true);
   testPipe(messages: 10, transform: false);
   testPipe(messages: 10, transform: true);
 }