Add SkShaderCodeDictionary::findOrCreateRuntimeEffectSnippet.

`findOrCreateRuntimeEffectSnippet` takes a pointer to the runtime effect
and returns a code-snippet ID associated with the runtime effect, with
matching uniform layout, etc. The SkShaderCodeDictionary will maintain a
persistent map from {sksl-hash, uniform set} to code-snippet ID.

http://go/runtime-effects-in-graphite

Change-Id: I9c51667aad96f850184899f3df00a8206a1fe354
Bug: skia:13405
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/552686
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
3 files changed