Add support for webp lossless compression

Bug: 713862
Change-Id: I8dcc6506338f3c54fb14a78620e7daaadadfedde
Reviewed-on: https://skia-review.googlesource.com/17073
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Matt Sarett <msarett@google.com>
5 files changed