GNOME shell shouldn't clear notifications when an app becomes focused
Apps like Chromium and Firefox create notifications with a reasonable expectation that the user should see them before they disappear. The current behavior is to clear notifications when the app became focused.
Here are some ways notifications could go missing:
Three web apps create notifications at around the same time. The user clicks on the first one, which focuses Chrome. The other 2 notifications never get shown and don't go to the message tray.
The user receives three notifications while they're away. The log into their machine and focus Chrome. They notice an icon disappear out of the corner of their eye. It was the notification tray indicating there were 3 unread notifications.
Three web apps create notifications which all go to the message tray. The user opens the message tray and notices they all have "OK" and "Cancel" buttons on them. They want to click OK on all of them. They click OK on the first one, which focuses Chrome, but also causes the other two to disappear.
The attached patch removes the unintuitive clear-notifications-on-focus behavior.