Investigate use of IOSurfaces.

[numist]

On Retina machines (and in any situation where there exist very large windows), it takes longer to fetch the window contents through Core Graphics' window services than it does to determine if the contents have changed. Both of these actions are still the most expensive things that Switch does as far as CPU time is concerned, and the use of IOSurfaces may obviate the need to poll the window server for window contents in many if not all cases.