[css-fonts-4] [varfont] Small variation ranges in @font-face descriptors should limit the effective range for the font

[litherum]

Migrated on behalf of @behdad from #517 (comment)

If @font-face declares a range narrower than what the font supports, then browser should clamp to the @font-face range indeed, even though the font supports wider.

[litherum]

Migrated on behalf of @svgeesus from #517 (comment)

Yes, this would be consistent with what we do with unicode-range for example - if the descriptors have a narrower range than what the font actually supports, then we enforce those restrictions. Because the stylesheet designer had some reason to do so (not liking glyphs in a particular unicode range / not liking the bolder weights so preventing them from being used).