title: Uncaught DOMException: Failed to execute 'postMessage' on 'Window': An object could not be cloned
body: <p>I'm trying to call </p>
  
  <pre><code>parent.postMessage(obj, 'whatever');
  </code></pre>
  
  <p>from within an iframe and I'm getting this error: <code>Uncaught DOMException: Failed to execute 'postMessage' on 'Window': An object could not be cloned.</code></p>