Remove deprecated string features.

tests/standalone/io/string_decoder_test.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.
 
 import "dart:io";
 
 void test() {
   // Code point U+10FFFF is the largest code point supported by Dart.
   //var decoder = _StringDecoders.decoder(Encoding.UTF_8);
   ListInputStream lis = new ListInputStream();
   lis.write([0xf0, 0x90, 0x80, 0x80]);  // U+10000
   lis.write([0xf4, 0x8f, 0xbf, 0xbf]);  // U+10FFFF
   lis.write([0xf4, 0x90, 0x80, 0x80]);  // U+110000
   lis.write([0xfa, 0x80, 0x80, 0x80, 0x80]);  //  U+2000000
   lis.write([0xfd, 0x80, 0x80, 0x80, 0x80, 0x80]);  // U+40000000
   lis.markEndOfStream();
 
   var sis = new StringInputStream(lis);
   sis.onData = () {
     var decoded = sis.read();
     Expect.equals(7, decoded.length);
 
-    var replacementChar = '?'.charCodeAt(0);
-    Expect.equals(0xd800, decoded.charCodeAt(0));
-    Expect.equals(0xdc00, decoded.charCodeAt(1));
-    Expect.equals(0xdbff, decoded.charCodeAt(2));
-    Expect.equals(0xdfff, decoded.charCodeAt(3));
-    Expect.equals(replacementChar, decoded.charCodeAt(4));
-    Expect.equals(replacementChar, decoded.charCodeAt(5));
-    Expect.equals(replacementChar, decoded.charCodeAt(6));
+    var replacementChar = '?'.codeUnitAt(0);
+    Expect.equals(0xd800, decoded.codeUnitAt(0));
+    Expect.equals(0xdc00, decoded.codeUnitAt(1));
+    Expect.equals(0xdbff, decoded.codeUnitAt(2));
+    Expect.equals(0xdfff, decoded.codeUnitAt(3));
+    Expect.equals(replacementChar, decoded.codeUnitAt(4));
+    Expect.equals(replacementChar, decoded.codeUnitAt(5));
+    Expect.equals(replacementChar, decoded.codeUnitAt(6));
   };
 }
 
 void testInvalid() {
   void invalid(var bytes) {
     ListInputStream lis = new ListInputStream();
     lis.write(bytes);
     lis.markEndOfStream();
     var sis = new StringInputStream(lis);
     sis.onData = () { throw "onData not expected"; };
     sis.onError = (e) { Expect.isTrue(e is DecoderException); };
     sis.onClosed = () { throw "onClosed not expected"; };
   }
 
   invalid([0x80]);
   invalid([0xff]);
   invalid([0xf0, 0xc0]);
 }
 
 void main() {
   test();
   testInvalid();
 }