def file_header(prog_name):
  """Returns the header to use on generated files."""
  return """// Copyright 2020 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.

// This is a generated file. Do not edit it! It was generated by:
//   {prog_name}
""".format(prog_name=prog_name)