Fix alpha in webp bug introduced with animation

Prior to 557fbbe05ba48bcc20be684d11fe0edfc24c87ba, if there was a
colorXform, we told libwebp to decode to unpremul, since
premultiplication is handled by the colorXform. In that CL, I handled
this in the case where the dst color type was not 8888 or when blending
with the prior frame, but not in the 8888/not blending with the prior
frame case.

Rearrange the code so we always tell libwebp to use BGRA_8888 unpremul
if there is a colorXform.

Change-Id: Ie1121bc65da6520af895e8eb72d53573426b7bd6
Reviewed-on: https://skia-review.googlesource.com/17781
Reviewed-by: Matt Sarett <msarett@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
1 file changed