Add fuzzing for decoding animated images

Add a new mode to decode all frames of an animated image. Use
incremental decoding, rather than getPixels, since the primary client
uses incremental decoding.

Do not decode animated as index 8, which is only supported for the
first frame.

Change-Id: I5d7ed1a81c1ef37df3701c483486d4beff0f62a7
Reviewed-on: https://skia-review.googlesource.com/5679
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
1 file changed