Whether online or offline, all information that Google Chrome contains is basically HTML, CSS, JS, while the offline message page is either the download or the history page. Other browsers would leave you high and dry when you go offline, but Chrome, thanks to Google team, must know that these small details are important.
The tiny canvas-based game is available through the excellent implementation of html5 support in Chrome. You can create your own game using html5/css/js. Google does check internet connectivity to see which page is up for loading, while the waiting game can be played until the internet is back online.