Remove deprecated string features.

tests/standalone/io/socket_close_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
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 //
 // Test socket close events.
@@ skipping 85 matching lines @@
     }
 
     void connectHandler() {
       _socket.onData = dataHandler;
       _socket.onClosed = closeHandler;
       _socket.onError = errorHandler;
 
       void writeHello() {
         int bytesWritten = 0;
         while (bytesWritten != 5) {
-          bytesWritten += _socket.writeList("Hello".charCodes,
+          bytesWritten += _socket.writeList("Hello".codeUnits,
                                             bytesWritten,
                                             5 - bytesWritten);
         }
       }
 
       _iterations++;
       switch (_mode) {
         case 0:
           _socket.close();
           proceed();
@@ skipping 106 matching lines @@
       List<int> b = new List<int>.fixedLength(5);
       data.readBytes += connection.readList(b, 0, 5);
       if (data.readBytes == 5) {
         whenFiveBytes();
       }
     }
 
     void writeHello() {
       int bytesWritten = 0;
       while (bytesWritten != 5) {
-        bytesWritten += connection.writeList("Hello".charCodes,
+        bytesWritten += connection.writeList("Hello".codeUnits,
                                              bytesWritten,
                                              5 - bytesWritten);
       }
     }
 
     void dataHandler() {
       switch (_mode) {
         case 0:
           Expect.fail("No data expected");
           break;
@@ skipping 137 matching lines @@
   var tests = 7;
   var port = new ReceivePort();
   var completed = 0;
   port.receive((message, ignore) {
     if (++completed == tests) port.close();
   });
   for (var i = 0; i < tests; i++) {
     new SocketClose.start(i, port.toSendPort());
   }
 }