Add a test for getFrameInfo on truncated data

Add a test for getFrameInfo on truncated data

Prior to e132e7be5f9108692254c37db592ea7611abbc15, calling getFrameInfo
on an SkGifCodec which was truncated before fully parsing the local
color map of the first frame would hit an assert. Add a test to verify
that the problem has been fixed.

Modify box.gif to use a local color map for the first (and only) frame.

Change-Id: I905afe60c0c6ecc82e251e00ef82b2e5b22975a3
Reviewed-on: https://skia-review.googlesource.com/13320
Reviewed-by: Chris Blume <cblume@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>