Migrating a block of dart 1 tests to dart 2

tests/language/closure_break1_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 ClosureBreak1 {
-  ClosureBreak1(this.field);
-  int field;
-}
-
-class ClosureBreak1Test {
-  static testMain() {
-    var o1 = new ClosureBreak1(3);
-    String newstr = "abcdefgh";
-    foo() {
-      o1.field++;
-      Expect.equals(8, newstr.length);
-    }
-
-    bool loop = true;
-    L:
-    while (loop) {
-      String newstr1 = "abcd";
-      var o2 = new ClosureBreak1(3);
-      foo1() {
-        o2.field++;
-        Expect.equals(4, newstr1.length);
-      }
-
-      Expect.equals(4, newstr1.length);
-      while (loop) {
-        int newint = 0;
-        var o3 = new ClosureBreak1(3);
-        foo2() {
-          o3.field++;
-          Expect.equals(0, newint);
-        }
-
-        foo2();
-        break L;
-      }
-    }
-    foo();
-    Expect.equals(4, o1.field);
-  }
-}
-
-main() {
-  ClosureBreak1Test.testMain();
-}