Remove deprecated string features.

tests/standalone/io/secure_server_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.
 
 import "dart:io";
 import "dart:isolate";
 
 const SERVER_ADDRESS = "127.0.0.1";
 const HOST_NAME = "localhost";
 
 class SecureTestServer {
   void onConnection(Socket connection) {
     numConnections++;
     var input = connection.inputStream;
     String received = "";
     input.onData = () {
       received = received.concat(new String.fromCharCodes(input.read()));
     };
     input.onClosed = () {
       Expect.isTrue(received.contains("Hello from client "));
       String name = received.substring(received.indexOf("client ") + 7);
-      connection.outputStream.write("Welcome, client $name".charCodes);
+      connection.outputStream.write("Welcome, client $name".codeUnits);
       connection.outputStream.close();
     };
   }
 
   void errorHandlerServer(Exception e) {
     Expect.fail("Server socket error $e");
   }
 
   int start() {
     server = new SecureServerSocket(SERVER_ADDRESS, 0, 10, "CN=$HOST_NAME");
     Expect.isNotNull(server);
     server.onConnection = onConnection;
     server.onError = errorHandlerServer;
     return server.port;
   }
 
   void stop() {
     server.close();
   }
 
   int numConnections = 0;
   SecureServerSocket server;
 }
 
 class SecureTestClient {
   SecureTestClient(int this.port, String this.name) {
     socket = new SecureSocket(HOST_NAME, port);
     numRequests++;
-    socket.outputStream.write("Hello from client $name".charCodes);
+    socket.outputStream.write("Hello from client $name".codeUnits);
     socket.outputStream.close();
     socket.inputStream.onData = () {
       reply = reply.concat(new String.fromCharCodes(socket.inputStream.read()));
     };
     socket.inputStream.onClosed = this.done;
     reply = "";
   }
 
   void done() {
     Expect.equals("Welcome, client $name", reply);
@@ skipping 30 matching lines @@
   EndTest = () {
     Expect.equals(CLIENT_NAMES.length, server.numConnections);
     server.stop();
     keepAlive.close();
   };
 
   for (var x in CLIENT_NAMES) {
     new SecureTestClient(port, x);
   }
 }