Hm, I take back my last comment, the issue seems to lie somewhere else. I don't see the issue anymore in a local build of todays mozilla-central, but reverting D204369 also doesn't bring it back.
Bug 1885949 Comment 6 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
Hm, I take back my last comment, the issue seems to lie somewhere else. I don't see the issue anymore in a local build of todays mozilla-central, but reverting D204369 also doesn't bring it back. Additionally, the check in D204369 was removed in `ShouldUpgradeHttpsFirstRequest` and not `PotentiallyDowngradeHttpsFirstRequest`, so it should not matter.