setStatPixelDataPostProcessor(pixelFunc) {
        this.gate.customStatPostProcesser = pixelFunc;
        return this;
    }
Specifies how to process raw pixel data from the custom stats texture maker into a more useful value.
@param {undefined|!function(pixelData: !Float32Array | Array.<!Float32Array>,
                            circuit: !CircuitDefinition,
                            col:!int,
                            row:!int)} pixelFunc
@returns {!GateBuilder}