Avoid additional FBO and render pass for the blurred background
WindowThumbnails are image providers meaning it can provide textures directly to ShaderEffects
layer.enabled is effectively a ShaderEffectSource meaning we render our single desktop background item into an offscreen texture to ultimately contain just our desktop background.
We can cut out the middle-man and use the DesktopBackground as a source directly saving a massive texture being generated.
I have no metrics but it's doing less and therefore should be faster. For the purposes of Nate's blog I'm going to claim it's a speed boost of 1 million percent.