SkStrike becomes SkScalerCache. It will eventually externalize
the memory accounting to SkStrikeCache::Node because the amount of
memory used by the scaler cache, and the overall strike cache memory
usage must be kept in sync.
Change-Id: Ia889f057d8138ec7f22f996e7ebb9d2441dea4ee
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/271018
Reviewed-by: Ben Wagner <bungeman@google.com>
