title: WebRTC - getting 'malformed constraints object' from Chrome but not Firefox
body: <p>I wonder what I'm doing wrong.</p>
  
  <p>I'm getting 'malformed constraints object' errors from this:</p>
  
  <pre><code>pc.createAnswer( function (answer) {
    ...
  }, fail, { offerToReceiveAudio: true, offerToReceiveVideo: true });
  </code></pre>
  
  <p>Any ideas?</p>