Revert "Delete SkImage::encode(Type)"

Revert "Delete SkImage::encode(Type)"

This reverts commit e48b4c550de60f3c2316f31125ee305c8df280ba.

Reason for revert: This method is used in Google3. See
https://test.corp.google.com/ui#id=OCL:138505330:BASE:138505351:1478611655214:39a02f0d

Original change's description:
> Delete SkImage::encode(Type)
>
> This doesn't appear to be used (fingers crossed).
>
> We're not ready to support color correct encodes (and tagging with
> color spaces) for all of the formats included in SkImageEncoder::Type.
>
> I think it's good to restrict this for now.
>
> BUG=skia:
>
> GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=4535
>
> Change-Id: I73000f3d7bff1af153786d766531a2cbc8c5b77a
> Reviewed-on: https://skia-review.googlesource.com/4535
> Reviewed-by: Mike Reed <reed@google.com>
> Commit-Queue: Matt Sarett <msarett@google.com>
>

TBR=msarett@google.com,brianosman@google.com,reed@google.com,reviews@skia.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I6fb880f10dcba7837647e9b5cabbc8cc2b8366f6
Reviewed-on: https://skia-review.googlesource.com/4538
Commit-Queue: Leon Scroggins <scroggo@google.com>
Reviewed-by: Leon Scroggins <scroggo@google.com>