Migrating a block of dart 1 tests to dart 2

tests/language_strong/closure_in_constructor_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";
-
-class A<T> {
-  var closure;
-
-  factory A.factory() => new A(() => new List<T>());
-
-  A([this.closure]) {
-    if (closure == null) {
-      closure = () => new List<T>();
-    }
-  }
-}
-
-main() {
-  Expect.isTrue((new A.factory()).closure() is List);
-  Expect.isTrue((new A()).closure() is List);
-  Expect.isTrue((new A<int>.factory()).closure() is List<int>);
-  Expect.isTrue((new A<int>()).closure() is List<int>);
-  Expect.isFalse((new A<int>.factory()).closure() is List<String>);
-  Expect.isFalse((new A<int>()).closure() is List<String>);
-}