Comment 6 for bug 1638610

(In reply to Justin Dolske [:Dolske] from comment #1)
> Huh, yeah. When I load http://n.mobzones.com/uk/m-s?offer=271, attempting to
> report the site does exactly what you describe. This isn't actually a
> problem specifically to Report a Site, entering "google.com" in the URL bar
> also results in the page somehow canceling that load and you end up on
> another spam page. (http://play.leadzupc.com/...).
>
> This seems pretty annoying, sites shouldn't be able to trap the user like
> this.
>
> Gijs/mconley: perhaps one of you could take a look to see what's happening?

This page has:

        $(window).on("beforeunload", function (e) {
            $(window).unbind("beforeunload");

            setTimeout(function () {
                window.location = url;
            }, 0);

            e.returnValue = message;
            return message;
        });

Boris, are there spec reasons we can't just stop navigation permanently as soon as we fire beforeunload, until either the page has been unloaded / destroyed, or the user explicitly decides to stay on the page?