This change will ultimately pull uniform color, and to a much lesser degree uniform coverage, into GPs.  There are still some loose ends because drawstate has the ability to override the GP, but fixing these cleanly will have to wait until we have deferred geometry in place and can make attribute / uniform decisions on the fly.

BUG=skia:

Review URL: https://codereview.chromium.org/746423007
whitespace change to context to force rebuild of skia

NOTREECHECKS=True
NOTRY=True
TBR=
BUG=skia:

Review URL: https://codereview.chromium.org/807663002