Add last() to SkZip

Change-Id: Ia1a1e58df38bd4865d4d3d389a6a75835b5e87df
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/254809
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
2 files changed