Disable the WIC encoder for jpegs

My fix from https://codereview.chromium.org/1791583002/ is not
sufficient.

WIC will only encode JPEGs if we pass in a bitmap in BGR
format.  For now, let's disable the WIC encoder on JPEGs
and fall back on SkImageEncoder_libjpeg.

This should fix the scaled-generator gm.
https://gold.skia.org/search2?query=source_type%3Dgm%26name%3Dscale-generator&include=false&head=true&unt=true&pos=false&neg=false&limit=100

BUG=skia:3969
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1823743002

Review URL: https://codereview.chromium.org/1823743002
1 file changed