Make deferred upload handling and draw recording be virtual interfaces implemented by GrOpFlushState.

The motivation for this is to allow other clients of GrDrawOpAtlas. Making GrMeshDrawOp::Target also be an abstract interface is somewhat incidental to this goal.

Bug: skia:
Change-Id: I0987adfa8a269aa2ca94147e933a2827d734c1cc
Reviewed-on: https://skia-review.googlesource.com/65121
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
16 files changed