c68d97e633
This makes the style system pass flags down to GetMetricsForCSSUnits to specify whether it needs the 'ch' or 'ic' units, which may trigger downloading additional font resources. There should be no change in user-visible behavior, except by observing (e.g. in the devtools network panel) what resources end up being fetched in an example like the reporter's. Differential Revision: https://phabricator.services.mozilla.com/D246780