Add Alpha Image GM

Change-Id: I835a59d9f8593e30db817dc8bd1d276af8c80cd7
Reviewed-on: https://skia-review.googlesource.com/24685
Reviewed-by: Hal Canary <halcanary@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
2 files changed