Remove deprecated string features.

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.
 
 part of dart.io;
 
 const String _webSocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 
 class _WebSocketMessageType {
   static const int NONE = 0;
@@ skipping 363 matching lines @@
           response.close();
         });
         return;
       }
       // Send the upgrade response.
       response.statusCode = HttpStatus.SWITCHING_PROTOCOLS;
       response.headers.add(HttpHeaders.CONNECTION, "Upgrade");
       response.headers.add(HttpHeaders.UPGRADE, "websocket");
       String key = request.headers.value("Sec-WebSocket-Key");
       SHA1 sha1 = new SHA1();
-      sha1.add("$key$_webSocketGUID".charCodes);
+      sha1.add("$key$_webSocketGUID".codeUnits);
       String accept = _Base64._encode(sha1.close());
       response.headers.add("Sec-WebSocket-Accept", accept);
       response.headers.contentLength = 0;
       response.detachSocket()
         .then((socket) {
           _controller.add(new _WebSocketImpl._fromSocket(socket));
         }, onError: (error) {
           _controller.signalError(error);
         });
     });
@@ skipping 88 matching lines @@
                 (value) => value.toLowerCase() == "upgrade") ||
             response.headers.value(HttpHeaders.UPGRADE).toLowerCase() !=
                 "websocket") {
           error("Connection to '$uri' was not upgraded to websocket");
         }
         String accept = response.headers.value("Sec-WebSocket-Accept");
         if (accept == null) {
           error("Response did not contain a 'Sec-WebSocket-Accept' header");
         }
         SHA1 sha1 = new SHA1();
-        sha1.add("$nonce$_webSocketGUID".charCodes);
+        sha1.add("$nonce$_webSocketGUID".codeUnits);
         List<int> expectedAccept = sha1.close();
         List<int> receivedAccept = _Base64._decode(accept);
         if (expectedAccept.length != receivedAccept.length) {
           error("Reasponse header 'Sec-WebSocket-Accept' is the wrong length");
         }
         for (int i = 0; i < expectedAccept.length; i++) {
           if (expectedAccept[i] != receivedAccept[i]) {
             error("Bad response 'Sec-WebSocket-Accept' header");
           }
         }
@@ skipping 172 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;
 }