We keep getting regressions (usually plugins) that only affect machines running in HiDPI mode. It would be great if we could run a set of reftests on a machine that has HiDPI enabled, at least for OSX. The most recent of these is bug 907792. Assuming the machines won't have an actual retina display attached, this may be useful: http://stackoverflow.com/questions/12124576/how-to-simulate-a-retina-display-hidpi-mode-in-mac-os-x-10-8-mountain-lion-on