Popups and other override-redirect windows are meaningless to everything
that depends on the ShellWindowTracker. Ignoring those windows will result
in less ShellApp::windows-changed signal emissions, and less activity in
the AppMenuButton and everything else that depends on them.
Reduces gnome-shell CPU activity while typing on the Epiphany addressbar,
as the pop up animation there results in a number of xdg_popup being
created and destroyed.
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/642https://gitlab.gnome.org/GNOME/mutter/issues/556
db9a7ea7a9