First step for modular output in fasta.

pkg/front_end/testcases/shaker/roots1.dart

Index: pkg/front_end/testcases/shaker/roots1.dart
diff --git a/pkg/front_end/testcases/shaker/roots1.dart b/pkg/front_end/testcases/shaker/roots1.dart
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index 0000000000000000000000000000000000000000..8d1f0297afe2d9c2d25d206ba15c1f1ad1ad445c
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+++ b/pkg/front_end/testcases/shaker/roots1.dart
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+// 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';
+
+/// Tree-shaker preserves APIs used anywhere in the library, there is no special
+/// root, and `main` is no special.
+foo() => toplevel();