[graphite] Keep baseVertex,baseInstance relative to offset specified when vertex buffers were bound

All of the draw variants except drawIndexed support all base arguments
as part of the draw call that is recorded. Updated drawIndexed to use
the "instance" version and draw 1 instance if the baseVertex is not 0.

Previously, if we bound the buffer at a non-zero offset, but then
passed in 0 for the base vertex/instance relative to that, it would
reset the vertex offset to 0. This also cuts down on the number of
commands recorded since draws will only correspond to one command.

Bug: skia:12466
Change-Id: I3eb95b02d33f2d1e9b36991a8b824012383bc192
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/474058
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Auto-Submit: Michael Ludwig <michaelludwig@google.com>
2 files changed