I have the following files:

a.html

<p id="p1">a.html</p>
<iframe src="b.html"></iframe> <!-- we have a realm here -->
<script>
  frames[0].postMessage("some data", "*");
</script>

b.html

<p id="p1">b.html</p>
<script>
  window.addEventListener("message", (event) => {
    console.log("event:", event);
  });
</script>

In the google chrome I don't see console.log message from b.html (I know what I should switch console tab for that), in the same moment in the firefox I see message. What's the matter?