Android : How is washingtonpost.com detecting mobile devices?

On my Nexus5 when I navigate to washingtonpost.com I am redirected to m.washingtonpost.com.

When using Chrome developer tools (v36) on Windows to emulate the Nexus5 (emulating the screen, user agent and sensors) and I navigate to washingtonpost.com I am redirected to www.washingtonpost.com.

So they must be using a mobile detection technique more sophisticated than Chrome's emulator.

How are they detecting mobile devices?

Is there any way to trick the site to showing the mobile site using chrome on a desktop?