Reason for revert:
Need to somehow get access to encoders in chrome -- link error on the roll since SkImageEncoder is not built as part of chrome.
Original issue's description:
> change pixel-serializer to support reencoding existing data
>
> Trying to evolve this interface so it can
> - support rich set of backend-encoders (including ones like ETC1 that can cheaply convert to KXT
> - allow for encoding images as well as bitmaps (e.g. for picture serialization)
> - perhaps replace SkImageEncoder as an API (assuming we create a factory that returns a serializer given a format)
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/13f48dc85aa68a60da66aaf39c93d527d11d1278TBR=scroggo@google.com,msarett@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:
Review URL: https://codereview.chromium.org/1371983003
c9e190ddac