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

It is confusing that this patch only has a special RTL case for the .details element and not for the .img and .unwatched elements. .img has a left set, but is not position:absolute, so the .left setting is probably ignored. .unwatched does have position:absolute, and you don't do anything with it here for RTL, so I'm guessing that it may be mis-positioned.

You're trying to patch what appears to be pretty crappy CSS.  Maybe this would be simpler if the three elements inside the .inner element were laid out with flexbox so that they can flow in the correct direction but the .details element can stretch to fill the available space.  Or, if you don't want to go flexbox, you should at least make sure that .unwatched works correctly and that .img does not have an unused left property or that it does have a position:absolute declaration. Or add a comment explaining the unusual combination of positioning styles.