Use WeakHashSet<const Font> instead of HashSet<const Font*> for extra safety.
Pull request: https://github.com/WebKit/WebKit/pull/17671
Committed 267905@main (1378f6bba165): <https://commits.webkit.org/267905@main> Reviewed commits have been landed. Closing PR #17671 and removing active labels.
<rdar://problem/115368763>