add "benchmark" mode to determine max/min luminance.

[Zeryth1]

It would be nice to have a feature for the HDR/SDR analysis shader to perform some kind of "benchmark":

You press a hotkey and all stats get reset,
you then collect data over a period of time.
Press hotkey again,
present statistics that were collected over that period of time.

This way you'll be able to see what the true minimum/maximum value was that the game displayed, instead of having to stare at the readout, which isn't updated every frame anyway. Could also be useful for gamut usage and average image brightness. This way users will be able to make more informed decisions on what to do.