Created attachment 8721935 [details] Screen Shot 2016-02-22 at 11.02.16.png See screenshot. I've only started seeing this since a few weeks ago or so, so it's probably a recent regression. It's probably related to switching to and/or from HiDPI (I think I see it at work, but not at home). FWIW, it appears like the click targets are still their usual size (i.e., trying to hit the tiny orange button closes the window -- which kind of sucks).
This definitely happens when disconnecting from my external monitor (i.e. Fx gets moved from non-HiDPI screen to HiDPI screen).