title: Receive postMessage from chrome new tab extension
body: <p>I have a popup (that is not made by me) that sends a postMessage for a login callback.</p>
  
  <p>In the new tab page (that opened the popup), I am unable to receive this message.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>window.addEventListener("message", receiveMessage, false);
  function receiveMessage(event)
  {
    console.log("MESSAGE RECEIVED!");
    console.log(event.data);
  }
  </code></pre>
  
  <p>^This does not work. </p>
  
  <p>(I am aware of the following API, chrome.runtime.onMessageExternal , but since the popup does not send a message via the chrome runtime, I cannot use this)</p>
  
  <p>How do I solve this problem?</p>