Fix unresolved classes issues in dart:io.

sdk/lib/io/websocket_impl.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.
 
 const String _webSocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 
 class _WebSocketMessageType {
   static const int NONE = 0;
   static const int BINARY = 1;
   static const int TEXT = 2;
@@ skipping 682 matching lines @@
       } else {
         _conn.detachSocket().socket.close();
         throw new WebSocketException("Protocol upgrade refused");
       }
       return;
     }
 
     if (!_isWebSocketUpgrade(response)) {
       _conn.detachSocket().socket.close();
       throw new WebSocketException("Protocol upgrade failed");
-      return;
     }
 
     // Connection upgrade successful.
     DetachedSocket detached = _conn.detachSocket();
     _socketConnected(detached.socket);
     if (_onOpen != null) _onOpen();
     _startProcessing(detached.unparsedData);
   }
 
   void _generateNonceAndHash() {
@@ skipping 150 matching lines @@
 
 class _WebSocketCloseEvent implements CloseEvent {
   _WebSocketCloseEvent(this._wasClean, this._code, this._reason);
   bool get wasClean => _wasClean;
   int get code => _code;
   String get reason => _reason;
   bool _wasClean;
   int _code;
   String _reason;
 }