css/css-fonts/variations/at-font-face-descriptors.html defines various expectations for what should happen with calc() expressions, but does not consistently do that, some are evaluated, some are not.

This issue is spun off of recent WebKit WPT test merge where expectations were changed from evaluated and clamped calc() results to unevaluated calc() results when reading back the descriptor.
WebKit/WebKit@c3e9369

Generally, the css-values specification suggest simplification:
https://w3c.github.io/csswg-drafts/css-values-4/#calc-simplification

We need to define what the serialized value of the font property-descriptors font-weight, font-stretch, font-style in
https://drafts.csswg.org/css-fonts-4/#font-prop-desc should be.