it's a little late but, here the solution that I found
app('url')->assetFrom('cdn-1', 'js/dropzone.js');
The url helper function can be used with no arguments to return the UrlGenerator also.
url()->assetFrom(...);
Laravel 5.5 Docs - Helpers - url()
An additional way to access it if you would like.
Sign in to participate in this thread!
Laravel
Laravel News
Laracasts
Laravel Podcast