If you use -webkit-radial-gradient() and omit the size/shape parameter, it should default to "ellipse cover", per the CSS3 spec. Instead, it appears to default to "circle cover".
<div style="width: 300px; height: 200px; border: thick solid; background: -webkit-radial-gradient(red, yellow);"></div>
It apears to not even be able to go into ellipse
Um, this has worked since I implemented the new gradients.
Oh, Linux. This is a Chromium bug then. Go file it at crbugs.