Revert "Change some platform libraries to use `part of URI`."

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";
+part of dart.io;
 
 const String _webSocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 const String _clientNoContextTakeover = "client_no_context_takeover";
 const String _serverNoContextTakeover = "server_no_context_takeover";
 const String _clientMaxWindowBits = "client_max_window_bits";
 const String _serverMaxWindowBits = "server_max_window_bits";
 
 // Matches _WebSocketOpcode.
 class _WebSocketMessageType {
   static const int NONE = 0;
@@ skipping 1266 matching lines @@
     return code != null &&
         (code < WebSocketStatus.NORMAL_CLOSURE ||
             code == WebSocketStatus.RESERVED_1004 ||
             code == WebSocketStatus.NO_STATUS_RECEIVED ||
             code == WebSocketStatus.ABNORMAL_CLOSURE ||
             (code > WebSocketStatus.INTERNAL_SERVER_ERROR &&
                 code < WebSocketStatus.RESERVED_1015) ||
             (code >= WebSocketStatus.RESERVED_1015 && code < 3000));
   }
 }