Add cyclic default-value test.

tests/language/cyclic_default_values_test.dart

+// Copyright (c) 2015, 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";
+
+bar([x = foo]) => x((_) => "bar");
+foo([y = bar]) => y((_) => "foo");
+
+foo2({f: bar2}) => f(f: ({f}) => "foo2");
+bar2({f: foo2}) => f(f: ({f}) => "bar2");
+
+main() {
+  var f = bar;
+  Expect.equals("bar", Function.apply(f, []));
+  Expect.equals("main", Function.apply(f, [(_) => "main"]));
+
+  f = bar2;
+  Expect.equals("bar2", Function.apply(f, []));
+  Expect.equals("main2", Function.apply(f, [], {#f: ({f}) => "main2"}));
+}