paint color -> shader

This means we can share programs with color shaders
whether they come through as a paint color or shader.

The GM now only ever JITs one program.

Change-Id: If61f9e7b79aa6b8fd1de7c16ff52f78bfd7dc4ec
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/252079
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
4 files changed