[e10s] Downloads button on about:home page isn't supported with enabled Electrolysis (multi-process mode) about download_panel_tweaker

[Infocatcher]

D'oh, how to detect browser with about:home without global content script:

var mm = Components.classes["@mozilla.org/globalmessagemanager;1"]
    .getService(Components.interfaces.nsIMessageListenerManager);
var listener = {
    receiveMessage: function(msg) {
        mm.removeMessageListener("AboutHome:RequestUpdate", this);
        var browser = msg.target;
        alert(browser.currentURI.spec);
    }
};
mm.addMessageListener("AboutHome:RequestUpdate", listener);

gBrowser.addTab("about:home");