We still have a few uses of BasicLayerManager/FrameLayerBuilder (even when WR is enabled) for widgets that want a super lightweight in-thread rendering.

We can rasterize a display list directly now, so we should add a new WindowRenderer (formerly LayerManager) implementation for widgets to hold that just runs this without any retaining/invalidation.

Depends on D120919

Depends on D120920

https://hg.mozilla.org/mozilla-central/rev/4149d596d03d
https://hg.mozilla.org/mozilla-central/rev/41176d476eb7
https://hg.mozilla.org/mozilla-central/rev/cf8a1175abd1

Backed out for causing Bug 1722935

backout: https://hg.mozilla.org/mozilla-central/rev/bdf05015fbffef15464dcad0cb7e5f0f7d309ebd

https://hg.mozilla.org/mozilla-central/rev/ce8f605d6920
https://hg.mozilla.org/mozilla-central/rev/e8299f044303
https://hg.mozilla.org/mozilla-central/rev/e505fffd43c3

Hi Matt, given the number of regressions already reported from this change and the incoming reports we're still getting, what do you think about backing this out from Beta92 so it has more Nightly bake time first? I've confirmed that it reverts cleanly.

(In reply to Ryan VanderMeulen [:RyanVM] from comment #9)

Hi Matt, given the number of regressions already reported from this change and the incoming reports we're still getting, what do you think about backing this out from Beta92 so it has more Nightly bake time first? I've confirmed that it reverts cleanly.

It's a tough call! We're hoping to remove a lot of the Layers code from Nightly93, so any regressions after that won't have a fallback option.

I think I'd prefer to try uplift the fix (up for review now, need to confirm that it's the same for all the regressions) if possible, since it's early in the beta cycle.