Replace StrikeRefs with SkStrikePromises

Change-Id: I68ee17e60776c3c3ca3dcbd98d734274625ed455
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/569197
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Herb Derby <herb@google.com>
4 files changed