Adding YUV decode plumbing from Skia to JPEG decoder

Adding the plumbing from the Skia derived classes through to the
Blink JPEG decoder. The Blink JPEG decoder and Skia code changes
needed were committed in:

Blink JPEG decoder changes:
https://codereview.chromium.org/418653002
https://codereview.chromium.org/480093003

Skia YUV to RGB conversion:
https://codereview.chromium.org/378503006
https://codereview.chromium.org/374743003

BUG=skia:1674

Review URL: https://codereview.chromium.org/496413002

git-svn-id: svn://svn.chromium.org/blink/trunk@181243 bbb929c8-8fbe-4397-9dbb-9b2b20218538