Chrome already does transparent updates to the browser, it's doubtful you would even notice that. But they are talking about a very limited application, only r

Chrome already does transparent updates to the browser, it's doubtful you would even notice that. But they are talking about a very limited application, only replacing the libraries where they know the exact version ahead of time (only the one's on Google's CDN). I would assume if the browser doesn't recognize a library, it just falls back to downloading it from the website.