Migrate block 162 to Dart 2.0.

tests/language_2/type_variable_closure3_test.dart

 // Copyright (c) 2016, 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";
 
 class A<T> {}
 
 class C<T> {
   a() {
     return () => new A<T>();
   }
 }
 
 main() {
   Expect.isTrue(new C<int>().a()() is A<int>);
   Expect.isFalse(new C<int>().a()() is A<String>);
 }