https://wpt.fyi/results/css/css-fonts/font-shorthand-serialization-font-stretch.html?label=master&label=experimental&aligned&view=subtest Only CSS3 keyword values for font-stretch can be serialized in the font shorthand, other values need to prevent font from serializing.
The test expects peculiar behavior, where you specify a value as a percentage and it serializes as the corresponding keyword. I implemented this behavior, but I am not sure the specification actually calls for it.
<rdar://problem/101217780>
Pull request: https://github.com/WebKit/WebKit/pull/5429
Committed 255628@main (eecfb48ef633): <https://commits.webkit.org/255628@main> Reviewed commits have been landed. Closing PR #5429 and removing active labels.