It looks like this is landing in Chrome. The
navigator.connection.type property will allow us to progressively enhance based on connection type:
A web application that makes use of a service worker to cache resources during installation might have different bundles of assets that it might cache: a list of crucial assets that are cached unconditionally, and a bundle of larger, optional assets that are only cached ahead of time when
There are potential security issues around fingerprinting that are addressed in this document.