GrFP can express distance vector field req., program builder declares variable for it

This update allows fragment processors to require a field of vectors to the nearest edge. This requirement propagates:

- from child FPs to their parent
- from parent FPs to the GrPaint
- from GrPaint through the PipelineBuilder into GrPipeline
- acessed from GrPipeline by GrGLSLProgramBuilder

GrGLSL generates a variable for the distance vector and passes it down to the GeometryProcessor->emitCode() method.

This CL's base is the CL for adding the BevelNormalSource API: https://codereview.chromium.org/2080993002

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2114993002

Committed: https://skia.googlesource.com/skia/+/4ef6dfa7089c092c67b0d5ec34e89c1e319af196
Review-Url: https://codereview.chromium.org/2114993002

0 files changed, 0 insertions, 0 deletions