Create SkUniform data in findOrCreateRuntimeEffectSnippet.

Graphite expects uniforms to be passed in as a span of SkUniforms.
When making a runtime effect, we now convert the SkRuntimeEffect's
`Uniform` data into SkUniforms as well.

I briefly looked at sharing a single uniform type, but
SkRuntimeEffect::Uniform is public API, so changing it is non-trivial,
and Uniform would not be usable as a direct replacement for SkUniform.
(Uniform is non-POD since it contains an SkString; SkUniform is POD
and we declare a bunch of them at global scope. Also, each class
represents types using a separate enum.)

Change-Id: Idef2141d3a4860529719382840a157b7b0c41643
Bug: skia:13457
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/553595
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
3 files changed