During a pull request review (https://github.com/WebKit/WebKit/pull/7615#discussion_r1048703175), Antti made the point that the CSSPropertyBlendingClient parameters which are always pointers ought to be reference since they're never null.
Actually, we'll reuse this bug for a more general refactoring of CSSPropertyAnimation::blendProperties() to deal with not only a reference for CSSPropertyBlendingClient but also a variant parameter for the property to deal with both standard properties and custom properties.
Pull request: https://github.com/WebKit/WebKit/pull/7678
Committed 257910@main (24ceea27a0d5): <https://commits.webkit.org/257910@main> Reviewed commits have been landed. Closing PR #7678 and removing active labels.
<rdar://problem/103396354>