GitLab

There have been a number of changes since the document was last updated.
Also clarify a few things.

This CL covers through checking the cache. I'll continue updating other
sections once this lands.

Bug: None
Change-Id: I5b205f81fb42c4d2727515fbc5d10f49d0b7736b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2141138
Commit-Queue: Matt Menke <mmenke@chromium.org>
Reviewed-by: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757874}