Update SkSpan to match the standard more closely

Change-Id: Iba5a9c24a34d5a08618b9182b476121bf6ce5ef9
Reviewed-on: https://skia-review.googlesource.com/139863
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Herb Derby <herb@google.com>
1 file changed