Comment 116 for bug 434476

(In reply to Chris Pearce (:cpearce) from comment #58)
> We want to inhibit the screensaver when video is playing,

I assume the "screen" wake lock is meant to take care of that.
http://hg.mozilla.org/mozilla-central/annotate/37f08ddaea48/content/html/content/src/HTMLVideoElement.cpp#l312