avoid build-timestamps in generated chromedriver source files

This change should allow cache hits with goma and ccache.

Change-Id: Ie9f1566d6f76a3de5fba5d039ff1a7f5b6f3b2ac
Reviewed-on: https://chromium-review.googlesource.com/c/1309778
Commit-Queue: Mostyn Bramley-Moore <mostynb@vewd.com>
Reviewed-by: John Chen <johnchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604258}

chrome/test/chromedriver/cpp_source.py

-# Copyright 2013 The Chromium Authors. All rights reserved.
+# Copyright 2018 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.
 
@@ -24,16 +24,13 @@ def WriteSource(base_name,
           variables will be available as globals.
   """
   copyright_header_template = (
-      '// Copyright %s The Chromium Authors. All rights reserved.\n'
+      '// Copyright 2018 The Chromium Authors. All rights reserved.\n'
       '// Use of this source code is governed by a BSD-style license '
       'that can be\n'
       '// found in the LICENSE file.\n\n'
-      '// This file was generated at (%s) by running:\n'
+      '// This file was generated by running:\n'
       '//     %s')
-  copyright_header = copyright_header_template % (
-      datetime.date.today().year,
-      datetime.datetime.now().isoformat(' '),
-      ' '.join(sys.argv))
+  copyright_header = copyright_header_template % (' '.join(sys.argv))
 
   # Write header file.
   externs = []