STR:

1. Be using Firefox (or Nightly) on Android, with the toolbar at the bottom and set to auto-hide on scroll (which are both part of our default settings).

2. View some LinkedIn profile page, e.g. this one for Mitchell Baker: https://www.linkedin.com/in/bakermitchell

(Note in case it matters: I'm doing this while not logged in to LinkedIn. In some browsers/configurations, the URL above redirects me to a "join or sign in before we'll show you anything" page -- but for whatever reason, specifically Firefox-for-Android and Firefox-Nightly-for-Android let me view profiles even when I'm not logged in.)

3. Scroll down to hide the toolbar. Notice that this reveals a fixed-position footer with text LinkedIn is better on the app. [Open]

4. Switch to another application or to your Android home screen, and then switch back to Firefox (using app-switcher or tapping icon on home screen).

ACTUAL RESULTS:
The contents of the footer-bar is missing -- it's just an empty gray bar. But if you scroll the page, the text comes back.

EXPECTED RESULTS:
Contents shouldn't go missing.

(CC dlrobertson who's working on similar bugs right now, I think; this might be a variant of some existing bug. Feel free to dupe if appropriate.)

Here's a reduced testcase, which requires less complex STR. I ran across it after noticing I could sometimes trigger the bug at LinkedIn in devtools by toggling a background-color on or off -- and that's what I do automatically in this testcase.

STR for testcase 1 are just to load the file and then scroll down to hide the dynamic toolbar, and wait a second or two. The footer ends up unexpectedly disappearing. (If I increase its height to be substantially taller than the dynamic toolbar, it doesn't disappear; so I think this is some sort of scenario where we improperly clip it / decline-to-repaint-it due to thinking it's covered up by the toolbar, or something like that.)

Interestingly: after I reproduce the bug on testcase 1 (i.e. footer missing)... if I turn my screen off and on again (i.e. lock/unlock my phone), the footer (text + background) is present and paints/blinks just fine.

But then if I scroll to show/hide the dynamic toolbar, it disappears again.

phone info: Pixel 4a, Android 13 (beta)
Tested Firefox 102.2.1 release as well as Firefox 105.0a1 Nightly. Both versions reproduce the bug (and behave as I've described/screencasted above, including e.g. the interesting quirk in comment 5).

At hiro's suggestion, I tested this with layout.display-list.retain set to false (disabling retained display lists).

That fixes it -- I can't repro any issues at original URL or at my testcase, under that configuration. hiro suggests that means this is indeed a dupe of the bug that dlrobertson is working on, which is I think bug 1772859.