Bugzilla

This is an extension of bug 2035796 which contained a second video of a semi-related bug to the original scenario, where clicking "Quit X Windows" from the OS dock icon closes each window separately, rather than sending a `quit-application-requested` signal, resulting in a race condition when the topmost window has a "heavy" page loaded. 

**Affected Platforms**

Windows and Linux. MacOS sends a single `quit-application-requested` signal and is unaffected.

**Preconditions**
* Have multiple FxE windows open
* Open at least one "heavy" site in a new tab on the topmost window
* `enterprise.prompt_on_signout` is set to `true`
* `browser.tabs.warnOnClose` is set to `false`

**Steps to reproduce**
1. From the menu bar, right click and select Quit x windows

**Expected result**
The signout dialog is displayed on the last window to close.

**Actual result**
The signout dialog is not displayed at all and all the windows are just closed.

Video: https://bugzilla.mozilla.org/show_bug.cgi?id=2035796#c1

This is an extension of bug 2035796 which contained a second video of a semi-related bug to the original scenario, where clicking "Quit X Windows" from the OS dock icon closes each window separately, rather than sending a `quit-application-requested` signal, resulting in a race condition when the topmost window has a "heavy" page loaded. 

**Affected Platforms**
Windows and Linux. MacOS sends a single `quit-application-requested` signal and is unaffected.

**Preconditions**
* Have multiple FxE windows open
* Open at least one "heavy" site in a new tab on the topmost window
* `enterprise.prompt_on_signout` is set to `true`
* `browser.tabs.warnOnClose` is set to `false`

**Steps to reproduce**
1. From the menu bar, right click and select Quit x windows

**Expected result**
The signout dialog is displayed on the last window to close.

**Actual result**
The signout dialog is not displayed at all and all the windows are just closed.