[css3-animations] calc() in keyframe selectors?

Kenny Lu raised an issue against V&U about specifying precisely where
calc() and other functions can be used.  One of the particular
questions he had was whether calc() was allowed in a keyframe
selector.

The definition of the syntax of @keyframes isn't clear whether it
specifically wants a PERCENTAGE token or just a <percentage> type
value.

I'd be okay if it wasn't allowed, but it's potentially useful, for the
same reason declaring percentage widths with calc() is useful - saying
"calc(100% / 7)" is clearer than "14.28%".

~TJ