title: Firebase notification onMessage not hitting when chrome tab is open but not active
body: <p>I have setup firebase messaging service and it works like a charm. Only problem is in <code>messaging.onMessage</code> function I have incremented count of notification on my page. Additionally I also have service worker setup that throws chrome notifications in background. </p>
  
  <p><a href="https://i.stack.imgur.com/oVSsy.png" rel="noreferrer"><img src="https://i.stack.imgur.com/oVSsy.png" alt="notification bell with counter"></a></p>
  
  <p>When my tab is <strong>open but not active</strong>, <code>messaging.onMessage</code> is not getting hit, but background handler service worker is hitting. So counter on my website is not increasing. When user goes to my website tab back again, it shows old notification count. That is creating bad UX. I am showing notifications list on click of count as like facebook shows.</p>