I also get "Failed to find test pattern on screen." in Safari with WebGL enabled on a Mid 2011 Mac Mini running 10.9 with dual monitors. View is set to "Actual

I also get "Failed to find test pattern on screen." in Safari with WebGL enabled on a Mid 2011 Mac Mini running 10.9 with dual monitors. View is set to "Actual Size", and I've tried moving the Safari window between monitors. Other scores - Chrome 30: 2.4/10. Firefox 24 and 25: 1.2/10.