Remove PDF JPEG shortcut, since it fails on grayscale JPEGs.

BUG=436079

Review URL: https://codereview.chromium.org/767343002
updated expectations from d476a176b774

BUG=skia:3180
TBR=reed@google.com
NOTRY=true

Review URL: https://codereview.chromium.org/773833002
skia: Prevent GL_RED from being used with MESA

MESA unfortunately doesn't support GL_RED or GL_RG when used with frame buffers.
Don't allow fTextureRedSupport to be set when using MESA.

BUG=skia:3181

Review URL: https://codereview.chromium.org/769073003