Filter flags to enable ARC on non ARC installed boards.

Ignore ARC availability related flags if ARC container is not installed
on the board at all. Move ARC related logic from libchromeos-ui to
chromeos-login

Showing TOS and opt-in relate UI on non ARC installed board is
misleading to user and make noise to our statics. Add filter to ignore
flags to enbale ARC in /ect/chrome_dev.conf.

BUG=b:36067509
TEST=Add unit test for libchromeos-ui for added/modified api.
TEST=Manual test. Modify /etc/chrome_dev.conf to enable ARC on link. No
ARC related UI is shown.

Change-Id: Ia9561acb6b2e609518c8d64c3b17fb9bcead9ec9
Reviewed-on: https://chromium-review.googlesource.com/464201
Commit-Ready: Long Cheng <lgcheng@google.com>
Tested-by: Long Cheng <lgcheng@google.com>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/474086
Commit-Queue: Long Cheng <lgcheng@google.com>
Trybot-Ready: Long Cheng <lgcheng@google.com>
4 files changed