With this change: https://chromium-review.googlesource.com/c/chromium/src/+/701974, we would always create the SkShader for a PaintShader at construction/record time to have this be cached on the PaintShader itself and make the creation thread-safe for raster. This suboptimal for OOP raster which will never use these shaders, and even for raster in the renderer where some of the recording may never be rasterized.

Eventually we want a shader cache, so the SkShader caching is external to the PaintShader. This would also be nice for cases where we create new SkShaders from PaintShaders to replace decodes, and which depend on the raster scale. So having a shader cache that can include these additional bits in the cache key would also be better.