Support additional mash shelf alignments.

mash/shelf/public/interfaces/shelf_constants.mojom

Index: mash/shelf/public/interfaces/shelf_constants.mojom
diff --git a/mash/shelf/public/interfaces/shelf_constants.mojom b/mash/shelf/public/interfaces/shelf_constants.mojom
new file mode 100644
index 0000000000000000000000000000000000000000..e281c47846d1abd556f6019730f8285fadaf2be7
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+++ b/mash/shelf/public/interfaces/shelf_constants.mojom
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+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+module mash.shelf.mojom;
+
+// These values match ash::ShelfAlignment.
+enum Alignment { BOTTOM, LEFT, RIGHT, };
+
+// These values match ash::ShelfAutoHideBehavior.
+enum AutoHideBehavior { ALWAYS, NEVER, HIDDEN, };