Hi,
in order to prevent whatever default action Notification's click event has (for example focus the tab which initiated the Notification), the click event should be cancelable so that .preventDefault() can be called. Some background https://bugzilla.mozilla.org/show_bug.cgi?id=874050&mark=25-26#c25 https://bugzilla.mozilla.org/show_bug.cgi?id=1009190#c0 -Olli
