[filter] Add ability to revert scrollbars

[anevins12]

Some websites try to emulate iOS devices by removing the scrollbar and relying on touch gestures, leaving people without gestures without important navigational aids.

Could we have an option to add the scrollbars back in? I'm thinking more along the lines of vertical scrolling.

[erikkroes]

A sort of reset on ::-webkit-scrollbar? Sounds very reasonable, thanks for the suggestion!