Bug 1671660 - Use CFNumber for the axis keys in the font variation dictionary. r=jrmuizel
Bug 1671660 - Use CFNumber for the axis keys in the font variation dictionary. r=jrmuizel

It seems that, starting with Big Sur, CTFontDescriptorCreateCopyWithAttributes
(and similar functions) no longer accepts axis names as the attribute dictionary
keys. Instead, the dictionary keys need to be CFNumbers of the axis tag.

Differential Revision: https://phabricator.services.mozilla.com/D93872

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/431f3b75086b61509dc3fa6a892c81c23e402074

servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender