In order to prevent the Customizer from using resources before it has been invoked, the bulk of the JS should be loaded lazily upon first invocation.
Created attachment 8588078 [details] [review] WIP pull-request (master) This is just part one. I moved all the controller/view initialization over to the MainController. Should make things easier to lazy-load now.
Comment on attachment 8588078 [details] [review] WIP pull-request (master) r- due only to the init marking pattern used. I left some other comments that are mostly just thinking out loud about where we are.
Created attachment 8590950 [details] [review] pull-request (master) This is an updated version of the PR that actually lazy-evals the WCs. It also addresses your previous comments about dealing with the promise flag.
Comment on attachment 8590950 [details] [review] pull-request (master) Looks good. I left some comments, but none of them are important to fix.
Addressed comments and landed on master: https://github.com/fxos/customizer/commit/be6c670b9375f4659485da099365d85de91c6283