Make String.charCodes a getter.

tests/corelib/collection_to_string_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.
 
 /**
  * Tests for the toString methods on collections and maps.
  */
 
 #library('collection_to_string');
 #import('dart:math', prefix: 'Math');
@@ skipping 279 matching lines @@
   return rand.nextInt(max);
 }
 
 /** Returns a random boolean value. */
 bool randomBool() {
   return rand.nextBool();
 }
 
 /** Returns the alphabetized characters in a string. */
 String alphagram(String s) {
-  List<int> chars = s.charCodes();
+  List<int> chars = s.charCodes;
   chars.sort((int a, int b) => a - b);
   return new String.fromCharCodes(chars);
 }