The "visibility" and "content-visibility" properties have a special type of discrete animation support which requires the progress to not be normalized to either 0 or 1 prior to calling the blend() method on their animation wrapper.
Pull request: https://github.com/WebKit/WebKit/pull/23498
Committed 273742@main (e4117be9080c): <https://commits.webkit.org/273742@main> Reviewed commits have been landed. Closing PR #23498 and removing active labels.
<rdar://problem/121926219>
This caused bug 270344.