Add 'Managed by' UI on chrome://history

Also updates the visual style of the footnote at the bottom of
chrome://history (the one that says "Your Google Account may have other
forms of browsing history...").

Adds a message for managed users at the bottom of the sidebar on the
chrome://history page page.

Enterprise users will now see a message that says "Your browser is
managed by your organization", with a link they can click to view a help
center article.

The new UI is hidden behind a flag so that most users don't see this WIP
feature just yet.

Bug: 893628
Change-Id: I127c83f421987914e7c137cdc7cdea3952e48b04
Reviewed-on: https://chromium-review.googlesource.com/c/1382811
Commit-Queue: Nicolas Ouellet-Payeur <nicolaso@chromium.org>
Reviewed-by: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624925}
15 files changed