GitLab

ScopedObservation is much safer and cleaner.

Change-Id: I189991b7aafb2cda41fa77a468b1f9a8a213fa10
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2522811
Commit-Queue: Darren Shen <shend@chromium.org>
Reviewed-by: Alexey Baskakov <loyso@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826210}