SkBitmap: simplify setPixels()

Change-Id: Ie0b1f3efd4739acce9da96a20352e5aec73697de
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/235020
Commit-Queue: Hal Canary <halcanary@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
1 file changed