[css-shapes-2][css-borders-4] corner-shape initial value

[jsnkuhn]

RESOLVED: Initial value of corner-shape is round

#10993 (comment)

Wouldn't the initial value for corner-shape have to be square/rect? to match most existing elements on the web? And that would mean "square/rect" would also need to be an option. So that we could do something like corner-shape: square angle square square;

(#6980 (comment))