Can you determine if Chrome is in incognito mode via a script?

Question

Is it possible to determine if Google Chrome is in incognito mode via a script?

Edit: I actually meant is it possible via user-script, but the answers assume JavaScript is running on a web page. I've re-asked the question here in regards to user scripts.

Answer 1

* Edit; the following no longer works in Chrome: *

Yes. The FileSystem API is disabled in incognito mode. Check out https://jsfiddle.net/w49x9f1a/ when you are and aren't in incognito mode.

Sample code:

    var fs = window.RequestFileSystem || window.webkitRequestFileSystem;
    if (!fs) {
      console.log("check failed?");
    } else {
      fs(window.TEMPORARY,
         100,
         console.log.bind(console, "not in incognito mode"),
         console.log.bind(console, "incognito mode"));
    }