Remove deprecated string features.

tests/standalone/io/socket_stream_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 92 matching lines @@
       _socket.inputStream.onClosed = closeHandler;
       _socket.onError = errorHandler;
 
       _iterations++;
       switch (_mode) {
         case 0:
           _socket.inputStream.close();
           proceed();
           break;
         case 1:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           _socket.outputStream.onNoPendingWrites = () {
             _socket.inputStream.close();
             proceed();
           };
           break;
         case 2:
         case 3:
         case 4:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           break;
         case 5:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           _socket.outputStream.onNoPendingWrites = () {
             _socket.outputStream.close();
           };
           break;
         case 6:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           break;
         case 7:
         case 8:
-          _socket.outputStream.write("Hello".charCodes);
+          _socket.outputStream.write("Hello".codeUnits);
           _socket.outputStream.onNoPendingWrites = () {
             _socket.outputStream.close();
           };
           break;
         default:
           Expect.fail("Unknown test mode");
       }
     }
 
     _socket = new Socket(SocketCloseServer.HOST, _port);
@@ skipping 103 matching lines @@
           break;
         case 2:
           readBytes(() {
             _dataEvents++;
             connection.inputStream.close();
           });
           break;
         case 3:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
             connection.outputStream.onNoPendingWrites = () {
               connection.inputStream.close();
             };
           });
           break;
         case 4:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
             connection.inputStream.close();
           });
           break;
         case 5:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
           });
           break;
         case 6:
         case 7:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
             connection.outputStream.onNoPendingWrites = () {
               connection.outputStream.close();
             };
           });
           break;
         case 8:
           readBytes(() {
             _dataEvents++;
-            connection.outputStream.write("Hello".charCodes);
+            connection.outputStream.write("Hello".codeUnits);
             connection.outputStream.close();
           });
           break;
         default:
           Expect.fail("Unknown test mode");
       }
     }
 
     void closeHandler() {
       _closeEvents++;
@@ skipping 107 matching lines @@
   var tests = 9;
   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());
   }
 }