Revert "Change image encode api to return sk_sp"

This reverts commit dc799550e2d9965aa5b7cda496465b2a76b310a5.

Reason for revert: need to fix sites in Document_none

Original change's description:
> Change image encode api to return sk_sp
> 
> Bug: skia:
> Change-Id: I238289bc630be27795cb1384955dd6e887597c05
> Reviewed-on: https://skia-review.googlesource.com/22208
> Commit-Queue: Mike Reed <reed@google.com>
> Reviewed-by: Florin Malita <fmalita@chromium.org>

TBR=scroggo@google.com,fmalita@chromium.org,reed@google.com

Change-Id: Id7f67027e5f1405a60fdbde29863cdf8daef0cb7
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/22280
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Mike Reed <reed@google.com>
13 files changed