Created attachment 268146 [details]
Scroll snapping is broken in RTL scrollable content. Test case attached.
We need to figure out of snap points are offsets (0 -> max) or positions (min -> max, possibly negative).
appendChildSnapOffsets() filters out negative offsets.
I think I fixed this.
Created attachment 417606 [details]
Updated test case
I've updated the test case to follow the modern version of the specification and I can confirm that this is working as expected. I'm going to close this bug for now and then we can open new bugs if we find more specific issues with RTL content.