When getting the computed style of a flex item that has a trimmed margin, it should be reported as 0
<rdar://problem/106559056>
Pull request: https://github.com/WebKit/WebKit/pull/11722
Committed 262708@main (c69be377e17c): <https://commits.webkit.org/262708@main> Reviewed commits have been landed. Closing PR #11722 and removing active labels.
Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/39434
Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/39554
The second WPT link is wrong and should not have been opened. Was meant to open an export for another bugzilla