[Bug] The toolbar appears on PWAs if backgrounded

[sv-ohorvath]

Steps to reproduce

1. Install and open a PWA (twitter, or 9gag)
2. Tap the task tray button.
3. Return to the app.
   1. Expected behavior
      The toolbar should never appear on PWA while you are navigating inside its scope.
   2. Actual behavior
      The custom tab toolbar is displayed on the PWA homescreen.
      *If you choose to open the page in Fenix, from the custom tab menu, the PWA task is closed.
   3. Device information

• Android device: Pixel 4 (Android 10), HTC Nexus 9 (Android 7.1.1)
• Fenix version: Beta 5.0, Nightly 4/30

LE:
The toolbar appears also if a doorhanger needs to be displayed: permission to access the camera/location for example.

┆Issue is synchronized with this Jira Task

[ekager]

Should be fixed by #10306 in master

[agi90]

This is still happening (screenshot from yesterdays Fenix nightly)

I think it happened after I reopened a PWA I hadn't used for a couple of hours.

[agi90]

I noticed that opening an instagram story triggers this. Not sure if there are more ways to trigger it.

[NotWoods]

I'm not able to reproduce this anymore. Can QA check if this is still an issue?

[agi90]

@NotWoods I can easily reproduce on the instagram PWA, open a story tap through the end and after you exit the PWA will have a toolbar.

[ekager]

Yeah, it now has to do with videos because on fullscreen, we are hiding the toolbar, but then when fullscreen ends, showing the toolbar again and don't treat PWAs differently right now. You can get it to show again by clicking on a link within the PWA.

[kbrosnan]

issue #10452 exists to deal with the full screen problem. Closing as a dupe of #10071 which was fixed by the pr Emily mentioned.