We have reports from the users (Tal is one of them) that after 2-day expiration time, if the tab with offline page is still open and user brings it to a foreground while offline, the tab will show "File not found" error.

Looking at the code at OfflinePageTabHelper, I see that if we are re-inflating the tab that was showing offline snapshot while offline, we go try to fetch the offline pages for the URL - and find none, since the URL is already file:// URL of an offline snapshot... Then we bail out and continue to show the page as is, simply failing to find a file.

Instead, we could have realized that the offline URL is for 'expired' page (which has no file but still kept in the database for few weeks) and instead map back to online URL and renavigate to that. It'll show dino page if offline, but it's better than a "file not found"...