Add Android ImageDecoder features to SkAnimatedImage

Bug: b/63909536
Bug: b/63908092

- Scale to an arbitrary size, using the decoding library if it supports
  it, and Skia otherwise
- Crop to a subset
- Post-processing with an SkPicture, to facilitate circle masks etc
- isRunning, to implement Animatable2 interface in Java

Change-Id: I13dbabee8e4a22e5cc193856aa3e94ce23ae4cb5
Reviewed-on: https://skia-review.googlesource.com/94660
Reviewed-by: Derek Sollenberger <djsollen@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
2 files changed