Reapply CL: first step for modular support in fasta

pkg/front_end/testcases/shaker/toplevel_reference.dart

Index: pkg/front_end/testcases/shaker/toplevel_reference.dart
diff --git a/pkg/front_end/testcases/shaker/toplevel_reference.dart b/pkg/front_end/testcases/shaker/toplevel_reference.dart
new file mode 100644
index 0000000000000000000000000000000000000000..12f211121509fa9d4dfd401bfe899dbd5e2ebe2f
--- /dev/null
+++ b/pkg/front_end/testcases/shaker/toplevel_reference.dart
@@ -0,0 +1,8 @@
+// Copyright (c) 2017, 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.md file.
+
+import 'lib/lib.dart';
+
+/// Direct references to toplevel members are preserved
+main() => toplevel();