It seems that some combination of the layout flipping in RTL locales and our magic ToC sidebar logic isn't working.
- set phone to arabic
- press ToC button (or swipe in)
- sidebar should slide in from the right (opposite side from usual)
- ToC should be visible
- empty gray space slides in from the right (opposite side from usual)
- no ToC is visible
Additionally we might want to switch the direction of the swipe detection when locale is RTL.