Migrate test block 30 + corelib portion of block 31 to Dart 2.0.

tests/corelib_2/unicode2_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.
 
 import 'package:expect/expect.dart';
 
 const String testPhrase = "The quick brown fox jumps over the lazy dog.";
 
 const List<int> testCodepoints = const <int>[
   84,
@@ skipping 57 matching lines @@
   Expect.stringEquals(testPhrase, new String.fromCharCodes(testCodepoints));
 }
 
 void testEmptyStringFromCharCodes() {
   Expect.stringEquals("", new String.fromCharCodes(<int>[]));
 }
 
 void testEmptyStringCharCodes() {
   Expect.listEquals([], "".codeUnits);
 }