title: TypeError: 'getUserMedia' called on an object that does not implement interface MediaDevices
body: <p>I'm trying to implement a webcam into a website using a video tag.
  It works in Chrome, but FireFox and IE return errors in the console.
  Anyone have any ideas why?
  Thank you!</p>
  
  <p>Code:</p>
  
  <pre><code>navigator.getMedia =    navigator.getUserMedia ||
                                  navigator.webkitGetUserMedia ||
                                  navigator.mediaDevices.getUserMedia ||
                                  navigator.msGetUserMedia ||
                                  OTPlugin.getUserMedia;
  </code></pre>
  
  <p>Firefox error:TypeError: 'getUserMedia' called on an object that does not implement interface MediaDevices.</p>
  
  <p>IE error: Unable to get property 'getUserMedia' of undefined or null reference</p>