Hide Assistant on deactivate.

This causes Assistant UI to be hidden but history to be retained for
5 min. Note that starting a metalayer session does not cause widget
deactivation.

Bug: b:114042400
Change-Id: Ie343095a5bbc661e091a21624d0fa6e9af0a0e6e
Reviewed-on: https://chromium-review.googlesource.com/1207730
Reviewed-by: Xiaohui Chen <xiaohuic@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#588938}
1 file changed