Using `wrapFunction` here makes sense, but we should revise it to not call the two functions `new` and `old`, since in this case they're reversed (because you want to call `intervalsChanged` after the original, instead of before).

Really what we've invented here with wrapFunction is [dojo/aspect](http://livedocs.dojotoolkit.org/dojo/aspect) (or more generally, aspect oriented programming) which lets you choose whether to provide before or after advice.