[css-values-5] Clarify how to determine the type of <percentage> in container-progress() and media-progress()

[cdoublev]

In container-progress() and media-progress(), I think the type of <percentage> should be determined according to the size/media feature instead of "the context":

<percentage>

If, in the context in which the math function containing this calculation is placed, <percentage>s are resolved relative to another type of value (such as in width, where <percentage> is resolved against a <length>), and that other type is not <number>, the type is determined as the other type, but with a percent hint set to that other type.

For example, width: calc(1px * container-progress(width from 0px to 100%)) should be invalid because the width size feature does not accept <percentage>.

Note: there is currently no container/media feature accepting <percentage>, if I am not mistaken.

[cdoublev]

Fixed in 4da8f9f.

Units in the progress start value and progress end value are interpreted as specified for the media feature (rather than as specified by the context the function is used in).