first start on a P3 GM

We don't have anything drawing colors outside sRGB,
but now that we've got SkPaint::setColor4f(), that's easy.

Looks like we have lots of work to do.

Pin GrColor4f floats before converting to unsigned.
Underflowing floats would get pinned to 255 spuriously
instead of to 0.  I think this fixes the failing CQ
bot, and the white square problem.

Change-Id: I866963ff026e6ab891b4c7d57decc43538000099
Reviewed-on: https://skia-review.googlesource.com/153640
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
8 files changed