For another, Autosync is extremely different from official solutions like the OneDrive sync utility for Mac and Windows. I have to preface this with two warnings: For one, some functionality is locked away behind an IAP purchase of at least $5, including full cloud storage sync. But if you absolutely need offline access to your cloud storage data on your Chromebook, there's an Android app that can help with that: Autosync.
While Chrome OS gained the ability to give you read-only access to third-party cloud storage, there is no official means of fully syncing files from there to your Chromebook. The only problem is that Chrome OS doesn't save a lot of data locally, and even the native Google Drive integration won't retain offline copies of files by default (though that can be changed for individual folders and files).
With Windows programs on the way to Chrome OS and Linux and Android apps already available, it's possible to get a lot of work done on a Chromebook while you're offline.
