Some of complicated gradient DRT tests fail:
fast/canvas/fillrect_gradient.html -- last gradient is not rendered properly
fast/canvas/gradient-add-second-start-end-stop.html -- render differs from FF and Chrome
fast/gradients/border-image-gradient.html -- render differs from Chrome
fast/gradients/border-image-gradient-sides-and-corners.html -- render differs from Chrome
fast/gradients/crash-on-zero-radius.html -- render differs from Chrome