Add SkJpegEncoder and SkWebpEncoder to public API

Bug: 713862
Change-Id: I05d8b3a506f817d63b0bc3ab3f9233e24bbe3be0
Reviewed-on: https://skia-review.googlesource.com/16233
Commit-Queue: Matt Sarett <msarett@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>
Reviewed-by: Mike Reed <reed@google.com>
5 files changed