Migrating a block of dart 1 tests to dart 2

tests/language_2/closure_self_reference_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';
 
 // Tests a self-reference of a closure inside a try/catch.
 // Dart2js must not try to box the closure-reference.
 
 main() {
   var counter = 0;
   inner(value) {
     if (value == 0) return 0;
     try {
       return inner(value - 1);
     } finally {
       counter++;
     }
   }
 
   Expect.equals(0, inner(199));
   Expect.equals(199, counter);
 }