Make String.charCodes a getter.

tests/corelib/string_test.dart

 // Copyright (c) 2011, 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.
 
 // TODO(ngeoffray): test String methods with null arguments.
 class StringTest {
 
   static testMain() {
     testOutOfRange();
     testIllegalArgument();
@@ skipping 266 matching lines @@
         Expect.equals(str[i], list[i]);
       }
     }
     test("abc");
     test("");
     test(" ");
   }
 
   static testCharCodes() {
     test(str) {
-      var list = str.charCodes();
+      var list = str.charCodes;
       Expect.equals(str.length, list.length);
       for (int i = 0; i < str.length; i++) {
         Expect.equals(str.charCodeAt(i), list[i]);
       }
     }
     test("abc");
     test("");
     test(" ");
   }
 }
 
 main() {
   StringTest.testMain();
 }