GitLab

Modify check for message center gaining activation to not
dereference the message center widget. There's a crash
caused by focus switching between the message center
and quick setting bubbles before the message center bubble's
constructor has exited.

Change-Id: Ia15acb47dc3806466a2f40a73e843333655e7953
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1860692
Commit-Queue: Ahmed Mehfooz <amehfooz@chromium.org>
Reviewed-by: Tim Song <tengs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705749}