Remove deprecated string features.

tests/standalone/io/secure_stream_test.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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // The --short_socket_write option does not work with external server
 // www.google.dk.  Add this to the test when we have secure server sockets.
 // See TODO below.
 
 import "dart:isolate";
 import "dart:io";
 
 void main() {
   ReceivePort keepAlive = new ReceivePort();
   SecureSocket.initialize();
   // TODO(3593): Use a Dart HTTPS server for this test.
   // When we use a Dart HTTPS server, allow --short_socket_write. The flag
   // causes fragmentation of the client hello message, which doesn't seem to
   // work with www.google.dk.
   var secure = new SecureSocket("www.google.dk", 443);
   List<String> chunks = <String>[];
   var input = secure.inputStream;
   var output = secure.outputStream;
 
-  output.write("GET / HTTP/1.0\r\nHost: www.google.dk\r\n\r\n".charCodes);
+  output.write("GET / HTTP/1.0\r\nHost: www.google.dk\r\n\r\n".codeUnits);
   output.close();
   input.onData = () {
     chunks.add(new String.fromCharCodes(input.read()));
   };
   input.onClosed = () {
     String fullPage = Strings.concatAll(chunks);
     Expect.isTrue(fullPage.contains('</body></html>'));
     keepAlive.close();
   };
 }