Create SkStrikePromises

Change-Id: I73f3745ffe055c8dfb8785b2a799f951af17936f
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/568287
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Herb Derby <herb@google.com>
3 files changed