Add tests to confirm that the scroll snap logic properly handles the following: 1. Inserting/removing elements into an existing scrollable region with snap points. 2. Marking elements 'display:none'
Also: 3. programmatically change overflow:scroll on ancestors of scroll-snap-coordinate elements
4. Snapping after layout changes Chrome does this now: https://web.dev/snap-after-layout/
<rdar://problem/60069355>
I believe that 1, 3, and 4 are currently covered, but there are no tests to check the behavior of css-scroll-snap when elements have 'display:none'.