GitLab

It took me a little while to figure out why the bounds in this function
were valid so I added some comments.

Change-Id: I1244b966dbb6b7984dfc4fbceaa7ed6a2f369aa3
Reviewed-on: https://chromium-review.googlesource.com/984958Reviewed-by: Balazs Engedy <engedy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548427}