title: BroadcastChannel testing in chrome developer tools console isn't working
body: <p>I am testing the <a href="https://developer.mozilla.org/en-US/docs/Web/API/BroadcastChannel" rel="nofollow noreferrer">BroadcastChannel</a> functionality and I'am having trouble. I open two Chrome windows and the dev tools for each. On the console I write:</p>
  <pre><code>const z = new BroadcastChannel('blarg')
  z.onmessage = function (ev) {console.log(ev)}
  </code></pre>
  <p>I can examine z and it has the function saved to the onmessage prop so it all looks good. However, when I test:</p>
  <pre><code>z.postMessage('sweet')
  </code></pre>
  <p>in one of the consoles, nothing shows in the other. I would expect since both Chrome windows are subscribed to the broadcast channel <code>blarg</code> and have a function to console log the message that is posted, I would see the message <code>sweet</code> to be shown in the other console but nothing happens.</p>
  <p>So two questions:</p>
  <p>Can't I test <code>BroadcastChannel</code> interface in the devtools console like this?</p>
  <p>If so, what am I missing about how BroadcastChannel works?</p>