1592079 - Remove thumbnails v3 migration code and associated flake-y test

Status: NEW

(Firefox :: New Tab Page, task, P3)

Description

[Mike Conley (:mconley) (:⚙️)]

The thumbnails v3 storage migration happened back in bug 239254 and shipped to users in Firefox 21.

I think we can go ahead and remove that migration code now.

This will also allow us to remove the flake-y test at https://searchfox.org/mozilla-central/rev/11d9c7b7fa82fdfb8ac2a8f0864e9d8d5fe2b926/toolkit/components/thumbnails/test/browser_thumbnails_storage_migrate3.js

That test is flake-y because the migration is kicked off-main-thread to a worker here: https://searchfox.org/mozilla-central/rev/11d9c7b7fa82fdfb8ac2a8f0864e9d8d5fe2b926/toolkit/components/thumbnails/test/browser_thumbnails_storage_migrate3.js#56

but the steps and checks that run after that don't wait until the migration has completed.

I originally updated the test to wait until after the migration had completed, and this actually caused the checks to fail, so this stuff might actually all be broken. However, since this migration has already taken place, that's probably okay.

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.