This seems rather pointless given HTLM5 ServiceWorkers. All of the benefits they're claiming with respect to local prefetching content for offline, instant use can be done with that spec. Even push-message content updates when the mobile browser isn't even running can be achieved. The only missing component is IOS support which might be possible to polyfill in via a hybrid.
I'm pretty sure Facebook knows about this, it seems like a platform lockin play.