Use patching for dart:io.

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 190 matching lines @@
                   }
                   break;
 
                 default:
                   throw new WebSocketException("Protocol error");
               }
             }
 
             // Hack - as we always do index++ below.
             index--;
+            break;
         }
 
         // Move to the next byte.
         index++;
       }
     } catch (e) {
       if (onClosed !== null) onClosed(WebSocketStatus.PROTOCOL_ERROR,
                                       "Protocol error");
       _state = FAILURE;
     }
@@ skipping 642 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;
 }