Move SkCodec::Origin into its own file

It is now used by SkPixmap and will soon be in SkJpegEncoder. No need
for those to depend on SkCodec.

Bug: 768878
TBR=reed@google.com
(reed@ already approved the API change in
https://skia-review.googlesource.com/60721)
Change-Id: If1a6e1d5b60a7a3d8c97818e15a48d28ba804668
Reviewed-on: https://skia-review.googlesource.com/61680
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>
8 files changed