Add support for font-variant-emoji in HarfBuzz callbacks
Add support for font-variant-emoji CSS property value in
HarfBuzzGetGlyph. Replaced ignore_variation_selectors flag with
VariationSelectorMode to also consider font-variant-emoji value.
Design doc: https://docs.google.com/document/d/1NyIKm0PnWUwX6j0smDwxDAPSUoiyBHPL95oH2lvjjpc/edit?usp=sharing
Bug: 40244183
Change-Id: Icd3bb2826a4f314ad5718edc69395f8b8d2224ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5534747
Reviewed-by: Dominik Röttsches drott@chromium.org
Commit-Queue: Munira Tursunova moonira@google.com
Cr-Commit-Position: refs/heads/main@{#1313410}