For this test case containingBlock->isFlexibleBox() is returning false although isFlexItem is returning true
<rdar://problem/107277206>
Pull request: https://github.com/WebKit/WebKit/pull/12040
Committed 262217@main (f73dcb9ce6b7): <https://commits.webkit.org/262217@main> Reviewed commits have been landed. Closing PR #12040 and removing active labels.