Remove deprecated string features.

samples/chat/chat_server_lib.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.
 
 library chat_server;
 import 'dart:async';
 import 'dart:io';
 import 'dart:isolate';
 import 'dart:json' as json;
 import 'dart:math';
@@ skipping 293 matching lines @@
   void _sendJSONResponse(HttpResponse response, Map responseData) {
     response.headers.set("Content-Type", "application/json; charset=UTF-8");
     response.addString(json.stringify(responseData));
     response.close();
   }
 
   void redirectPageHandler(HttpRequest request,
                            HttpResponse response,
                            String redirectPath) {
     if (_redirectPage == null) {
-      _redirectPage = redirectPageHtml.charCodes;
+      _redirectPage = redirectPageHtml.codeUnits;
     }
     response.statusCode = HttpStatus.FOUND;
     response.headers.set(
         "Location", "http://$_host:$_port/${redirectPath}");
     response.contentLength = _redirectPage.length;
     response.add(_redirectPage);
     response.close();
   }
 
   // Serve the content of a file.
@@ skipping 23 matching lines @@
       file.openRead().pipe(response);
     } else {
       print("File not found: $fileName");
       _notFoundHandler(request, response);
     }
   }
 
   // Serve the not found page.
   void _notFoundHandler(HttpRequest request, HttpResponse response) {
     if (_notFoundPage == null) {
-      _notFoundPage = notFoundPageHtml.charCodes;
+      _notFoundPage = notFoundPageHtml.codeUnits;
     }
     response.statusCode = HttpStatus.NOT_FOUND;
     response.headers.set("Content-Type", "text/html; charset=UTF-8");
     response.contentLength = _notFoundPage.length;
     response.add(_notFoundPage);
     response.close();
   }
 
   // Unexpected protocol data.
   void _protocolError(HttpRequest request, HttpResponse response) {
@@ skipping 302 matching lines @@
     }
   }
 
   int _timeRange;
   List<int> _buckets;
   int _currentBucket;
   int _currentBucketTime;
   num _bucketTimeRange;
   int _sum;
 }