Detect if Chrome DevTools are open

Here's an interesting snippet taken from the validation code in the new Discover DevTools course prepared by Google and CodeSchool (check it out, btw, it's awesome!):

function () {
    console.profile(); 
    console.profileEnd(); 
    if(console.clear) { console.clear() };
    return console.profiles.length > 0;
}

It exploits the fact that CPU profiles aren't actually run if DevTools are closed. Looks hacky but it works!

P.S. The same trick is also reported to work with Firefox+Firebug.

UPD This no longer works starting from Chrome 29 due to removal of console.profiles from window.console API. Related Chromium issue: https://codereview.chromium.org/15816002