GitLab

This CL adds protection to ensure a notification can not be
added after ash has been destroyed

Bug: 1164631
Change-Id: I497a142b1f05990a855ce837408adf3660247e19
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2639161Reviewed-by: Justin DeWitt <dewittj@chromium.org>
Commit-Queue: Ahmed Mehfooz <amehfooz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845331}