Also update doc.

Bug: chromium:973992
Change-Id: I59a27935d2bcd438df025945b885384b1d5b0792
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1665328
Commit-Queue: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>