title: how to send cross domain post message in safari?
body: <p>According to <a href="http://caniuse.com/#feat=x-doc-messaging" rel="nofollow noreferrer">canIuse</a> Safari 9 support Cross domain postMessage but when I try to send message to different domain I've got exception about origin.</p>
  
  <p>I have code like this:</p>
  
  <pre><code>var input = document.getElementsByTagName('input')[0];
  // this line throw exception
  var win = document.getElementsByTagName('iframe')[0].contentWindow;
  a.onclick = function() {
      var obj = {message: input.value};
      sysend.broadcast('foo', obj);
      // proxy to send message to other domains using hidden iframe
      win.postMessage(JSON.stringify({key: 'foo', data: obj}), "*");
  };
  </code></pre>
  
  <p>the page that show this error is <a href="http://jcubic.pl/sysend.php" rel="nofollow noreferrer">http://jcubic.pl/sysend.php</a></p>