window.onbeforeunload works when close tab, but doesn't work when close browser

Question

Sorry mi english.

I'm using Firefox 38, JSF 2.0, Primefaces 4 and Primefaces Extensions 1.2, in Chrome works perfectly

my code is

window.onbeforeunload = function(){ rcCloseWindow(); };

I need to call a managed bean method ONLY when browser is closed

<pe:remoteCommand name="rcCloseWindow" actionListener="#{loginManagedBean.whatever}" async="true"/>

This works in firefox when i close tab, but not when i close browser, in Chrome works perfectly

Any idea? Thanks.