[css-shapes] Optional radius arguments for ellipse shapes

Hi Alan, et al.

Rob (cc'd) and I were talking about parsing of ellipse shapes[1], and we noticed that the grammer seems to say that both <shape-radius> arguments or none must be supplied, when the spec makes it sound like it would be valid for just one <shape-radius> to be supplied, causing the second to default to closest-side[2]. I believe that the grammar is what is incorrect in this case, but can you clarify?

Thanks,
Bem

[1]: http://dev.w3.org/csswg/css-shapes-1/#funcdef-ellipse
[2]: http://dev.w3.org/csswg/css-shapes-1/#typedef-shape-radius