[scroll-animations-1] Define how the source member of a ScrollTimeline corresponding to a scroll() timeline is updated #8204
Description
https://drafts.csswg.org/scroll-animations-1/#dom-scrolltimelineoptions-source
I might be misunderstanding how all this works but if I define an anonymous scroll timeline in CSS using the scroll() notation, then inspect the corresponding Animation object's timeline I assume I can inspect the ScrollTimeline.source to see what element root or nearest resolved to.
If I then modify the CSS of an ancestor element such that root or nearest resolve to a different element, is the same ScrollTimeline object updated? If so do we need to specify a procedure for updating the source of a ScrollTimeline? Or is a new ScrollTimeline minted? In either case we'd need to define it because the result would be observable.