The default libjpeg library is libjpeg_turbo, except for Chrome OS. This
change switches the Chrome OS build to use IJG jpeg for the login screen.
The intended outcome is to have everything use libjpeg_turbo except for
JPEGCodec in ui/gfx.

ChromeUtilityMsg_RobustJPEGDecodeImage:
  Send decodes to JPEGCodec which then uses chromium_ijg_ mangled libjpeg to
  decode JPEGs.
ChromeUtilityMsg_DecodeImage:
  Send decodes to blink WebImage. Any JPEGs would then be decoded with
  libjpeg_turbo mangled with chromium_jpeg_.

User login code avatar/user_image_manager_impl.cc and
wallpaper/wallpaper_manager.cc currently setup UserImageLoader with
ImageDecoder::ROBUST_JPEG_DECODE.

Tests were run on a Peppy (Haswell 2955U), using the image_decoding benchmark
in telemetry.

ImageDecoding_avg.image_decoding.html?jpg:
Stock (ms): 166.98 166.80 163.03
Patch (ms):  78.95  73.27  78.23

TBR=cpu@chromium.org
BUG=413712
TEST=
$ cd ./tools/perf
$ ./run_benchmark --remote=${IP} \
                  --browser=cros-chrome-guest \
                  run image_decoding.image_decoding_measurement

Review URL: https://codereview.chromium.org/569623002

Cr-Commit-Position: refs/heads/master@{#328812}