Use the new web_socket_channel package.

lib/src/barback/admin_server.dart

 // Copyright (c) 2014, 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.
 
 import 'dart:async';
 import 'dart:io';
 
-import 'package:http_parser/http_parser.dart';
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:shelf_web_socket/shelf_web_socket.dart';
+import 'package:web_socket_channel/web_socket_channel.dart';
 
 import '../io.dart';
 import '../log.dart' as log;
 import 'asset_environment.dart';
 import 'base_server.dart';
 import 'web_socket_api.dart';
 
 /// The web admin interface to pub serve.
 // TODO(rnystrom): Currently this just provides access to the Web Socket API.
 // See #16954.
@@ skipping 39 matching lines @@
 
   /// Creates a web socket for [request] which should be an upgrade request.
   void _handleWebSocket(WebSocketChannel channel) {
     _webSockets.add(channel);
     var api = new WebSocketApi(channel, environment);
     api.listen()
         .whenComplete(() => _webSockets.remove(channel))
         .catchError(addError);
   }
 }