Add policy ChannelDowngradeBehavior

Add a policy called ChannelDowngradeBehavior to control whether to
powerwash and rollback or wait for new updates on channel downgrade.
This policy will be used in Chrome (for UI) and Chrome OS (update
engine).

Bug: 1110808
Change-Id: I71b91670f2e2fe0f077587a6b8c4b3e80d2e8dc3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2324623
Commit-Queue: Miriam Polzer <mpolzer@google.com>
Reviewed-by: Sergey Poromov <poromov@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#793544}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 3349ec211e2cd5534f215814f6bc6900572d68f0
1 file changed