Graphite: Rough out DrawCommandList and BoundsManager

Device will own and manage a BoundsManager, which it will use to decide
the sort and test Z's that it passes to the DrawCommandList in its
draw() implementations.

DrawCommandList might end up being owned by the SDC, with the SDC
exposing a similar drawing API. There will need to be some mechanism to
end a DrawCommandList and start a new one (the list moves into an
SDCTask). This would either happen from an external flush call, or in
the rare case where the representable Z values are exhausted and we
have to insert a depth buffer clear and start a new task that depends
on the prior one.

Bug: skia:12466
Change-Id: I892b631037dc801eb94da2462683c9701afa281b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/451599
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
3 files changed