Found a problem during looking into Bug 1714838.

https://treeherder.mozilla.org/jobs?repo=try&revision=d4994e0f6b71269844236284185f66ded546ac7f

Is this a regression? Can you check if it was working in earlier versions?

(In reply to Jeff Muizelaar [:jrmuizel] from comment #3)

Is this a regression? Can you check if it was working in earlier versions?

Sometimes the bug could not happen then I tried the following several times. Then Bug 739096 seems to trigger the problem.

./mach mozregression --good 2021-04-12 --bad 2021-05-01 --pref gfx.webrender.software:true gfx.webrender.software.d3d11:false layers.gpu-process.enabled:false -a about:support

2:33.81 INFO: No more integration revisions, bisection finished.
2:33.81 INFO: Last good revision: d735e197d708d85d9b7e7cb1ea3609bdc4f27bd6
2:33.81 INFO: First bad revision: 7387be4b195f3f266410d8faafbaf80f8176e293
2:33.81 INFO: Pushlog:
https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=d735e197d708d85d9b7e7cb1ea3609bdc4f27bd6&tochange=7387be4b195f3f266410d8faafbaf80f8176e293

I confirmed the problem on beta(90).

https://hg.mozilla.org/mozilla-central/rev/49f374ded227

Please request uplift when you get a chance.

Comment on attachment 9226759 [details]
Bug 1715953 - Add flush DrawTarget

Beta/Release Uplift Approval Request

• User impact if declined: Rendering is broken on Windows when Software WebRender without D3D(RenderTextureHostSWGL) is used.
• Is this code covered by automated tests?: Yes
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: none
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): The change just added flush DrawTarget.
• String changes made/needed: none

Comment on attachment 9226759 [details]
Bug 1715953 - Add flush DrawTarget

approved for 90.0b9

https://hg.mozilla.org/releases/mozilla-beta/rev/ea56ae3d9b29