Make the strike cache hash table own the strike

Make the ownership explicit by using the hash
table.

Change-Id: I3e1520091e755010c71a9b497af62a64636dc5bd
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/272722
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Herb Derby <herb@google.com>
2 files changed