[css-overflow-5]: allowing tab to access non-current items causes mismatch in forward vs. backward tab order

[smhigley]

This issue can be observed on the Cards example in the gallery: https://chrome.dev/carousel/horizontal/cards/

If the carousel is set to any marker but the first, the behavior tabbing forwards through the carousel does not match the behavior tabbing backwards.

The solution I would lean towards would be to ensure that tabbing does not reach any carousel item that is not fully in the viewport, so that tab alone can never trigger slide changes.