IMHO, this belongs inside the _processedAppTree function.  Moving it out of `appAndDependencies` makes that function easier to grok (since you can just assume that this thing being pulled in is the `processed app tree`).  In other words, by using a meaningful name (`_processedAppTree`), you can understand what `appAndDependencies` is doing without needing to understand the broccoli processing that is done there.