Using staging buffers for uploads of d3d static buffers.

Change-Id: I0da997bd373860ed5e729159abf1b9a0878d2ba4
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/305570
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: Jim Van Verth <jvanverth@google.com>
4 files changed