First step for modular output in fasta.

pkg/front_end/testcases/shaker/lib/lib.dart

+// 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 file.
+
+/// Shaker tests verify that portions of this file are preserved and that the
+/// rest is tree-shaken.
+library lib;
+
+toplevel() => null;
+
+class _A {}
+
+class B extends _A {}
+
+class C extends _A {}
+
+class K {}
+
+class M2 {}
+
+class M3 {}
+
+class M1 extends Object with M2 implements M3 {}
+
+class Bound {}
+
+class Base<T extends Bound> {}
+
+typedef T MyTypedef<T>(T arg);
+
+class F {
+  K field;
+}