This would require callers to seperate logic for desugaring CSS properties
(and resolving relative units) from parsing CSS tokens to a style tree! This
would also help implement calc(), and somewhat generically handle inherit.
Can be implemented as a PropertyParser decorator.
It occurs to me that this could be easily hand-tested by writing a commandline program which displays computed values (relative to initial values) for a style declaration.
That might even be useful program! Though ofcourse it shouldn't replace automated testing.