Migrate block 162 to Dart 2.0.

tests/language_2/type_variable_closure_test.dart

 // Copyright (c) 2013, 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 C<T> {
   C.foo() {
     x = (a) => a is T;
   }
   C.bar() {
     x = (a) => a is! T;
   }
   C.baz() {
     x = (a) => a as T;
   }
   var x;
 }
 
 main() {
   Expect.isTrue(new C<int>.foo().x(1));
   Expect.isFalse(new C<int>.foo().x('1'));
   Expect.isFalse(new C<int>.bar().x(1));
   Expect.isTrue(new C<int>.bar().x('1'));
   Expect.equals(new C<int>.baz().x(1), 1);
   Expect.throws(() => new C<int>.baz().x('1'));
 }