I'm assuming it uses WebRTC; it won't let me into the site past the front page as I don't use Chrome.
Which is sad, since the Mozilla and Chrome teams work closely on developing WebRTC and ensuring compatibility.
Edit: found some more info in the source of that page. This is their configuration guide:
1. Open the URL chrome://flags the latest version of Google Chrome.
2. Scroll to the bottom of the page and enable "Enable screen capture support in getUserMedia()
3. Restart browser - that's it
So, yes, WebRTC.
