I wonder whether we can drop the following deprecated moz-prefixed values from overflow shorthand: * -moz-scrollbars-none * -moz-scrollbars-horizontal * -moz-scrollbars-vertical People can already get the effect of these values via standard CSS values. Other vendors obviously never support these keywords, and thus there shouldn't be web compat issue. Also, we don't have any internal use of them except in tests. It seems they are somehow widely used in addons, so I'm not completely sure whether we should keep them.

It seems stylo has already implemented this, so it no longer needs to block that, but I guess in long term we still want to remove non-standard things, so keep this bug open.