I don't see service workers here: http://cdn.polyfill.io/v1/docs/features/ or here https://github.com/Financial-Times/polyfill-service/tree/mas...

Emulating service worker with App Cache sounds... very hard. Do you have more info on this specifically? I've got an app that's using app cache now and I'd like to gracefully transition it to using service workers as they become available.