When you inform, for example: transition: -ms-transform 1s ease, transform 1s ease; for an element, its transform-origin is algo transitioned. A working example: https://jsfiddle.net/3umthzxh/6/ It worked on the last version of Safari bundled with macOS 10.12.3, after upgrading to macOS 10.12.4 the bug appeared. The bug is in WebKit 12603.1.30.0.34, r215681 too.
<rdar://problem/31827243>
I think we're falling back to transitioning "all". Not sure if that's per spec.
Spec says: "If one of the identifiers listed is not a recognized property name or is not an animatable property, the implementation must still start transitions on the animatable properties in the list using the duration, delay, and timing function at their respective indices in the lists for transition-duration, transition-delay, and transition-timing-function. In other words, unrecognized or non-animatable properties must be kept in the list to preserve the matching of indices." so we're wrong here.
Created attachment 309072 [details] patch
Comment on attachment 309072 [details] patch r=me
Comment on attachment 309072 [details] patch Clearing flags on attachment: 309072 Committed r216204: <http://trac.webkit.org/changeset/216204>
All reviewed patches have been landed. Closing bug.