Add a whitespace.txt file

Bug: 869249
Change-Id: Iab9eeade2427255ce167fb524b11e0e3f691a685
Reviewed-on: https://chromium-review.googlesource.com/1161382Reviewed-by: Frank Barchard <fbarchard@chromium.org>
Commit-Queue: Ryan Tseng <hinoka@chromium.org>
Commit-Queue: Frank Barchard <fbarchard@chromium.org>

whitespace.txt

+Use this file to trigger builds