Migrated test block 29 to Dart 2.0

tests/corelib/string_to_lower_case_test.dart

-// Copyright (c) 2014, 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 "package:expect/expect.dart";
-
-void testOneByteSting() {
-  // Compare one-byte-string toLowerCase with a two-byte-string toLowerCase.
-  var oneByteString =
-      new String.fromCharCodes(new List.generate(256, (i) => i)).toLowerCase();
-  var twoByteString =
-      new String.fromCharCodes(new List.generate(512, (i) => i)).toLowerCase();
-  Expect.isTrue(twoByteString.codeUnits.any((u) => u >= 256));
-  Expect.equals(oneByteString, twoByteString.substring(0, 256));
-}
-
-void main() {
-  testOneByteSting();
-}