README.md/HACK.md tweakage, again.

Change-Id: I10ca564b7a7c0d36ca46854301c6d45e509361e7
Reviewed-on: https://chromium-review.googlesource.com/175871
Reviewed-by: Robert Ginda <rginda@chromium.org>
Tested-by: Robert Ginda <rginda@chromium.org>