Fix crash during serialization of the font shorthand.
It's not clear whether calc() expressions should be converted into
font keywords; not doing it seems like the most consistent handling,
given that calc() is never converted into literals anywhere else,
but it clashes with existing practice.
Bug: 40946458
Change-Id: I60c4fa354ec016ceeb872b7dabbef14d69412814
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6057817
Commit-Queue: Steinar H Gunderson sesse@chromium.org
Reviewed-by: Anders Hartvoll Ruud andruud@chromium.org
Cr-Commit-Position: refs/heads/main@{#1389776}