Bug 1095826 - [RTL][Video] Thumbnail images do not appear

It seems to me that with the flexbox, you shouldn't have to use absolute positioning and a really wide margin and a width:calc().  Ideally, you'd just use the flex: property to make this a flexible child so that it fills up the available space.  (Having said that, however, I'll confess that I have not used flexboxes myself yet)