ccpr: Simplify triangle corners

Modifies triangle corner shaders to just approximate their coverage with
linear values that ramp to zero at bloat vertices outside the triangle.

For the vertex backend, since corners now have the same fragment shader
as the rest of the triangle, we fold them in with the other steps and
draw triangles in a single pass.

The geometry backend still draws triangles in two passes, as there is
not an apparent performance advantage in combining them.

Updates SampleCCPRGeometry to better visualize this new geometry by
clearing to black and drawing with SkBlendMode::kPlus.

Bug: skia:
Change-Id: Idf8df8ff715dfab7ac91a07b914f65c08e46010b
Reviewed-on: https://skia-review.googlesource.com/113287
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>

0 files changed, 0 insertions, 0 deletions