Fix some analyzer warnings in dart:io.

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;
 
 const String _webSocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 
 class _WebSocketMessageType {
   static const int NONE = 0;
@@ skipping 808 matching lines @@
   StreamSubscription listen(void onData(message),
                             {void onError(error),
                              void onDone(),
                              bool cancelOnError}) {
     return _controller.stream.listen(onData,
                                      onError: onError,
                                      onDone: onDone,
                                      cancelOnError: cancelOnError);
   }
 
-  Duration get pingnterval => _pingInterval;
+  Duration get pingInterval => _pingInterval;
 
   void set pingInterval(Duration interval) {
     if (_writeClosed) return;
     if (_pingTimer != null) _pingTimer.cancel();
     _pingInterval = interval;
 
     if (_pingInterval == null) return;
 
     _pingTimer = new Timer(_pingInterval, () {
       if (_writeClosed) return;
@@ skipping 34 matching lines @@
            (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));
   }
 }