I don't have serialization working yet, but I have enough of the
plumbing to sketch out an API. It seems simplistic, but notice it
requires access to the SkStrikeClient.
Change-Id: I29f046b62f20c635cee86f0666e8112ac3097f16
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/507837
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Herb Derby <herb@google.com>