After tweaking various things I figured out that the problem is the Adblock Plus add-on. I'm still not sure if the change was made by Adblock, Facebook or Opera, but in any case when I disabled Adblock Plus and refreshed, the video controls were back. Just to make sure I enabled it and refreshed again, yup, video controls were gone. I tried some other Facebook videos and it was the same thing. I reported it to Adblock Plus, and will just leave the add-on disabled on FB until they get this glitch fixed.