[Bug] Screenshot is not blocked when starting the app

[Mugurell]

The Settings -> Private browsing -> Allow screenshots in private mode is not enforced when starting the app.
If putting the app to background and resuming it (in most cases) the screenshots are blocked - as it should have happened from the beginning.

Steps to reproduce

Have Settings -> Private browsing -> Allow screenshots in private mode disabled

1. Open the app and go tot the private tabs screen

   • Optional step: Open the list of open tabs in tabs tray
   • Take a screenshot

2. Come back to app homescreen from a private tab

   • Optional step: Open the list of open tabs in tabs tray
   • Take a screenshot

Expected behavior

• A message from Android saying that screenshots are not allowed

Actual behavior

• Screenshots are possible

To note

When putting the app in background and resuming the FLAG_SECURE gets set (not all the times) so now one cannot take record the screen while in private mode.

Video showing these cases (use the android message / screenshot as indicators of when screenshots are blocked or not):

FLAG_SECURE.not.enforced3.mov

┆Issue is synchronized with this Jira Task

[sflorean]

Verified as fixed on Nightly 2/10 with LG G7 (Android 8.1.0)

[Nickoriginal]

Reproducible in Firefox 89.1.1, 90.0.0-beta.6 and Nightly 91.0a1 2021-06-30T17:07:09.023

2021-07-01_09-20-37_001.mp4

2021-07-01_09-58-12_001.mp4

2021-07-01_09-55-52_001.mp4

[Nickoriginal]

@Mugurell, you can confirm this bug on your device(s), and, if possible, reopen it?

[Mugurell]

I see that screenshots are blocked in the browser (which this ticket was for)
but not in the tabs tray, for which we have an open ticket - #17855

[Nickoriginal]

Thanks!