[canvaskit] Add some APIs for speed and clients

isVolatile = false may make drawing some meshes faster.

saveLayer can be used to draw more rich effects.

Bug: skia:
Change-Id: If26f30cebba2a45f7519dd934eab02597cd6d2dc
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/197851
Reviewed-by: Kevin Lubick <kjlubick@google.com>
5 files changed