It makes it easier to process the license automatically like other files.
The text of the license in tools/chromiumos/LICENSE matches
https://spdx.org/licenses/BSD-3-Clause.html exactly.
#!/usr/bin/env python3
+# SPDX-License-Identifier: BSD-3-Clause
# -*- coding: utf-8 -*-
# Copyright 2017 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
+# found in the LICENSES/BSD-3-Clause.txt file.
"""Autosuspend udev rule generator