[Bug 1930982] [NEW] Firefox 89: webrender breaks videos on Raspberry Pi

[David Griffin]

Public bug reported:

Firefox 89 enabled the Webrender framework by default. Unfortunately,
the GFX drivers on a Pi 4 seem to be non-compliant in a way that breaks
videos - specifically, there will be a lot of primary coloured artefacts
in videos. My guess is that other Raspberry Pi's will also be affected,
but I don't have the hardware available to test. Setting gfx.webrender
.force-disabled to True fixes the issue, so it's fairly clear where it
lies.

Mozilla doesn't seem to provide official builds for Raspberry Pi's (or
Linux/Arm in general), so I think this is an issue to fix in these
packages, rather than upstream. The quick solution would to just set
gfx.webrender.force-disabled to True for the Pi-platforms and be done
with it, but there may be better solutions I don't know about.

Additioal info:
Ubuntu release: 21.04
Firefox package: firefox/hirsute-security,hirsute-updates,now 89.0+build2-0ubuntu0.21.04.1 arm64
Steps to reproduce: Play a video on Youtube, watch the coloured blocks appear. Then set gfx.webrender.force-disabled to True and restart to verify the fix.

** Affects: firefox (Ubuntu)
     Importance: Undecided
         Status: New

** Description changed:

  Firefox 89 enabled the Webrender framework by default. Unfortunately,
  the GFX drivers on a Pi 4 seem to be non-compliant in a way that breaks
  videos - specifically, there will be a lot of primary coloured artefacts
  in videos. My guess is that other Raspberry Pi's will also be affected,
  but I don't have the hardware available to test. Setting gfx.webrender
  .force-disabled to True fixes the issue, so it's fairly clear where it
  lies.
  
  Mozilla doesn't seem to provide official builds for Raspberry Pi's (or
- Linux/Arm in general), so I think this is an issue with these packages,
- rather than upstream. The quick solution would to just set gfx.webrender
- .force-disabled to True for the Pi-platforms and be done with it, but
- there may be better solutions I don't know about.
+ Linux/Arm in general), so I think this is an issue to fix in these
+ packages, rather than upstream. The quick solution would to just set
+ gfx.webrender.force-disabled to True for the Pi-platforms and be done
+ with it, but there may be better solutions I don't know about.
  
  Additioal info:
  Ubuntu release: 21.04
  Firefox package: firefox/hirsute-security,hirsute-updates,now 89.0+build2-0ubuntu0.21.04.1 arm64
  Steps to reproduce: Play a video on Youtube, watch the coloured blocks appear. Then set gfx.webrender.force-disabled to True and restart to verify the fix.

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Title:
  Firefox 89: webrender breaks videos on Raspberry Pi

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