Remove deprecated string features.

pkg/serialization/test/serialization_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.
 
 library serialization_test;
 
 import 'dart:json' as json;
 import 'package:unittest/unittest.dart';
 import 'package:serialization/serialization.dart';
 import 'package:serialization/src/serialization_helpers.dart';
@@ skipping 136 matching lines @@
   });
 
   test('Iteration helpers', () {
     var map = {"a" : 1, "b" : 2, "c" : 3};
     var list = [1, 2, 3];
     var set = new Set.from(list);
     var m = keysAndValues(map);
     var l = keysAndValues(list);
     var s = keysAndValues(set);
 
-    m.forEach((key, value) {expect(key.charCodes[0], value + 96);});
+    m.forEach((key, value) {expect(key.codeUnits[0], value + 96);});
     l.forEach((key, value) {expect(key + 1, value);});
     var index = 0;
     var seen = new Set();
     s.forEach((key, value) {
       expect(key, index++);
       expect(seen.contains(value), isFalse);
       seen.add(value);
     });
     expect(seen.length, 3);
 
@@ skipping 571 matching lines @@
   }
   findValue(String key, Map state) {
     var answer;
     for (var each in state.keys) {
       var value = state[each];
       if (value == key) return each;
     }
     return null;
   }
 }