Use libjpeg-turbo for YUV->RGB conversion in jpeg encoder

This remove the previous codepath, which performed a less
accurate conversion to YUV.

It actually faster to use the more accurate conversion, now
that we have updated to libjpeg-turbo.

z620 Performance Speed-Up:
mandrill.jpg (512x512): 1.13x
color_wheel.jpg (128x128): 1.12x

This should fix:
https://buganizer.corp.google.com/u/0/issues/28161384
https://buganizer.corp.google.com/u/0/issues/21891795

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1886183002

Review URL: https://codereview.chromium.org/1886183002
1 file changed