Commander: dismiss on focus loss

The deleted test was removed because the functionality it was tested
is now impossible to trigger in normal use and it was causing issues
on Linux.

Bug: 1014639
Change-Id: I95423d28c5cbf7bb278a416dde8284485f6b6075
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3143873


Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/main@{#919279}