Do color correction of vertex colors in GPU drawVertices

SkColor vertex colors need to be linearized (from sRGB),
and possibly converted from sRGB gamut to destination gamut.

Bug: skia:6659
Change-Id: I2b1b1dd0fa5938519693f56a728fed5957f13fd5
Reviewed-on: https://skia-review.googlesource.com/17534
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
6 files changed