Migrating a block of dart 1 tests to dart 2

tests/language/closure_break2_test.dart

-// Copyright (c) 2011, 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.
-// Dart test for closures.
-
-import "package:expect/expect.dart";
-
-class ClosureBreak2 {
-  ClosureBreak2(this.field);
-  int field;
-}
-
-class ClosureBreak2Test {
-  static testMain() {
-    var o1 = new ClosureBreak2(3);
-    String newstr = "abcdefgh";
-    foo() {
-      o1.field++;
-      Expect.equals(8, newstr.length);
-    }
-
-    bool loop = true;
-    L:
-    while (loop) {
-      String newstr1 = "abcd";
-      Expect.equals(4, newstr1.length);
-      while (loop) {
-        int newint = 0;
-        Expect.equals(4, newstr1.length);
-        break L;
-      }
-    }
-    foo();
-    Expect.equals(4, o1.field);
-  }
-}
-
-main() {
-  ClosureBreak2Test.testMain();
-}