nsGlobalWindow::SetFullScreen() (on Windows at least) causes the top level browser window to be lowered and then raised. So if we call SetFullScreen() after the top-level window has been lowered (say from the "exit fullscreen on alt+tab" event listener), we will lower and then raise the window, causing the window to be drawn as if it's been raised (focused, and the window manager's active window), even though it's not the window manager's active window.

https://bugzilla.mozilla.org/show_bug.cgi?id=1472046 Move all DOM bugs that haven’t been updated in more than 3 years and has no one currently assigned to P5. If you have questions, please contact :mdaly.