Instead of keeping a per-FontGroup cache of the previously used fallback
font, cache this value in the caller of `FontGroup::find_by_codepoint`.
The problem with caching this value in the `FontGroup` is that it can
make one layout different from the next.
Still, it is important to cache the value somewhere so that, for
instance, Chinese character don't have to continuously walk through the
entire fallback list when laying out. The heuristic here is to try to
last used font first if the `Script`s match. At the very least this
should make one layout consistent with the next.
Fixes#35704.
Fixes#35697.
Fixes#35689.
Fixes#35679.
Signed-off-by: Martin Robinson <mrobinson@igalia.com>
f949d2adc8