title: WebUSB getDevices empty list
body: <p>Running Chrome 56.0.2924.76 (64-bit) on Windows 10 PRO Version 1511 (OS Build 10586.753). Have enabled experimental-web-platform-features on chrome, running it with flag --disable-webusb-security and as administrator. I try to get USB device list on localhost (using https) with getDevices but I get empty list, although chrome://device-log is showing me plenty of devices. What could be the issue?</p>
  
  <pre><code>navigator.usb.getDevices().then(function(devices){
      console.log(devices);
  });
  // console outputs []
  </code></pre>