Fixes cascade issues when applying both -webkit-transform-style and transform-style (see bug 239579), and simplifies code as well given the FIXME was never addressed.
Created attachment 458449 [details] Patch
You will need to update the expectations for these tests: fast/css/getComputedStyle/computed-style.html fast/css/getComputedStyle/computed-style-without-renderer.html imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml.html imported/w3c/web-platform-tests/css/cssom/getComputedStyle-detached-subtree.html svg/css/getComputedStyle-basic.xhtml
Created attachment 458456 [details] Patch
Committed r293524 (250055@trunk): <https://commits.webkit.org/250055@trunk>
<rdar://problem/92412686>
Found 5 new test failures: fast/css/getComputedStyle/computed-style-without-renderer.html, fast/css/getComputedStyle/computed-style.html, imported/w3c/web-platform-tests/css/css-cascade/all-prop-initial-xml.html, imported/w3c/web-platform-tests/css/cssom/getComputedStyle-detached-subtree.html, svg/css/getComputedStyle-basic.xhtml