Helper ast node sequences must not wrongly grab ownership of the enclosing

tests/language/src/Closure2Test.dart

Index: tests/language/src/Closure2Test.dart
===================================================================
--- tests/language/src/Closure2Test.dart	(revision 0)
+++ tests/language/src/Closure2Test.dart	(revision 0)
@@ -0,0 +1,17 @@
+// 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.
+
+bounce(fn) {
+  return fn();
+}
+
+demo(s) {
+  var i, a = bounce(() => s);
+  return a;
+}
+
+main() {
+  Expect.equals("Bounce!", demo("Bounce!"));
+}