bug 799523 pt 1 - avoid mixing CSS-pix and device-pix coordinates in GetWindowInnerRectCenter. r=bz
bug 799523 pt 2 - convert device pixels to Cocoa display pixels when synthesizing native mouse event. r=smichaud
bug 799523 pt 3 - work around fullscreen window-size error (bug 729011) by calculating center in integer CSS pixels instead of device pixels. r=bz