https://bugs.webkit.org/show_bug.cgi?id=20289

Sanity check screenDepthPerComponent to ensure it is returning the number of bits per color rather than the screen depth (e.g. 24).
Should be rgb(0, 0, 0): rgb(0, 0, 0)
Should be rgb(0, 128, 0): rgb(0, 128, 0)