Don't all JS engines compile to machine code these days?
If the special thing is cross-compiling to machine code on the server and sending binary code to be run on the client, then that might be new - but it's scary from a security perspective.
I'd like to see some evidence that transmitting ARM binary code of JS is faster than transmitting the original JS and then JITting it to ARM. The binary alone will be a magnitude larger at least than the original source.
Even if it's bigger over the wire, they might still save on total rendering time and/or battery life.
They seem to be suggesting that these optimisations are intelligent and vary with circumstances, so they don't have to work every time as long as they can predict when the right time to turn them on is.
