limits property
Sixteen taps and two attachments unless the constructor said otherwise
— gfx-50n. Two is a parameter because the device it stands in for
cannot be asked: Impeller on OpenGL ES aborts rather than refusing, so
there is no way to run the no-MRT path on the hardware that has it.
This fake answers what a pass was opened with; CpuDevice, which
takes the same number, answers what came out the other end as pixels.
Implementation
@override
final DeviceLimits limits;