In adition to transforms/opacity/etc, text animators can target
per-glyph opacity.
Change-Id: I6ab63a6e49a64beaf63fc955f0b672a5b8ba84ba
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/272886
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
