We should simply concatenate two filter values when animating with additivity like we do for transform.
Pull request: https://github.com/WebKit/WebKit/pull/6734
Committed 256955@main (bbb772a0a698): <https://commits.webkit.org/256955@main> Reviewed commits have been landed. Closing PR #6734 and removing active labels.
<rdar://problem/102612994>