Dawn: implement a ring buffer for uniform uploads.

GrDawnGpu vends ring buffer slices out of a persistent (larger) buffer.

GrDawnProgramDataManager::setData() now returns a BindGroup containing
the (possibly new) UBO bindings, as well as the texture and sampler
bindings.
Change-Id: Id6694d6f44a815cfbffe4293779bf9bf558a2365
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/235866
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Stephen White <senorblanco@chromium.org>
10 files changed