(For example, we'll often be able to avoid rebinding the vertex and
index buffers at new offsets by just keep counting upwards between draws,
if the vertex format is the same but other state changed)
Want to get rid of direct accesses to GPUState in modules that may be reused in
my future next-gen backends, that will reformat display lists into command lists that will
then be optimized and executed, out of sync with the real GPUState.
Candidate modules that may be reused in full are Framebuffer and Depal, possibly TextureCache to some degree.
