To me this is the same as caching `new Extent(0.0, 0.0, 0.0, 0.0)`.  Let's [disagree and commit](http://www.competingonexecution.com/2009/05/how-to-get-things-done-disagree-and-commit/).  Onward.  :+1: 

If I change `createSampler` later, I'll update this.