+++ This bug was initially created as a clone of Bug #1525641 +++

The WPT reftest css/css-transforms/transform3d-matrix3d-005.html is failing.

Test case: https://searchfox.org/mozilla-central/source/testing/web-platform/tests/css/css-transforms/transform3d-matrix3d-005.html

Reftest analyzer view: https://hg.mozilla.org/mozilla-central/raw-file/tip/layout/tools/reftest/reftest-analyzer.xhtml#logurl=https://queue.taskcluster.net/v1/task/SsHso2dKRbCup-k22gpffg/runs/0/artifacts/public/logs/live_backing.log&only_show_unexpected=1

Try push: https://treeherder.mozilla.org/#/jobs?repo=try&group_state=expanded&revision=0ec8e6c560cd86f7d0d19d41cede6014fe9dd546

It's currently marked FAIL for all of the QR platforms at https://searchfox.org/mozilla-central/rev/e00ea598e52bbb35f8c45abf9c2eade17962bb5e/testing/web-platform/meta/css/css-transforms/transform3d-matrix3d-005.html.ini

This is fairly straightforward - handling transformations (non-preserve3d) with W != 1. It's easy to make a wrench reftest and debug from there.

Pushed by nerli@mozilla.com:
https://hg.mozilla.org/integration/autoland/rev/4febe6f32b23
ensure that w~=1 when assuming a transform is just a translation. r=gw

https://hg.mozilla.org/mozilla-central/rev/4febe6f32b23

Comment on attachment 9057673 [details]
Bug 1525642 - ensure that w~=1 when assuming a transform is just a translation.

Beta/Release Uplift Approval Request

• Feature/Bug causing the regression: None
• User impact if declined: Correctness issues with 3d transforms when using WebRender
• 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): Simple patch with good tests. Only affects WebRender
• String changes made/needed:

Comment on attachment 9057673 [details]
Bug 1525642 - ensure that w~=1 when assuming a transform is just a translation.

Low risk correctess issue with WebRender and we ship our first version of WebRender in 67. Uplift approved for 67 beta 11, thanks!

https://hg.mozilla.org/releases/mozilla-beta/rev/68224b37ba35