Gave some content_shell constants unique names and better docs

content_shell wants to replicate a chome constant at several
places which caused collisions in jumbo build experiments. This
give the replicas unique names and fixes the documentation which
was a bit outdated.

Bug: 886902
Change-Id: Ibf65de50bb2f938392fcecc910d70a4c4182c87d
Reviewed-on: https://chromium-review.googlesource.com/1233715
Commit-Queue: Daniel Bratell <bratell@opera.com>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593143}
3 files changed