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This includes the basic functionality for commander (sans multi-step
commands).

Styling is WIP.

Bug: 1014639
Change-Id: I809d11c851df0b4849bdb3c8ac0930ed37308d76
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2468680Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: dpapad <dpapad@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#821515}