Multithread SkStrike test

Change-Id: Id034c7fb35e1c0d6ae70a19d612b955d25c570af
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/269900
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
2 files changed