Fix WIC encoder to support kJPEG_Type

(1) Add support for kJPEG to WIC
(2) Add encoding test.
(3) Turn on WIC jpeg encoder on Windows and CG jpeg
    encoder on Mac.

A follow-up may make Skia's encoders the default on all
platforms.  But, in order to do that, I think we need
to write better encoding unit tests for CG and WIC.

BUG=skia:3969
BUG=skia:5632
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2245453002

Review-Url: https://codereview.chromium.org/2245453002
3 files changed