In https://chromium-review.googlesource.com/c/chromium/src/+/1103549, in order to fix the notification bug a temporary fix is used.

We should investigate to see if it's possible to have a cleaner/more generic way to hide notifications from the UI and avoid unimportant updates. (In this case the update invoked by Prefetched pages with their thumbnail updated.

Possible ways:
- Introduce a new method in observer interface for thumbnail updates.
- Have a more generalized way to identify uninterested offline items and avoid showing notification for them.