nsIWebBrowser
the chrome object must also implement nsiembeddingsitewindow.
... see also nsibasewindow nsicontextmenulistener nsidomwindow nsiembeddingsitewindow nsiinterfacerequestor nsishistorylistener nsitooltiplistener nsiuricontentlistener nsiweakreference nsiwebbrowserchrome nsiwebbrowserchromefocus nsiwebprogresslistener ...

nsIWebBrowserChromeFocus
embedding/browser/webbrowser/nsiwebbrowserchromefocus.idlscriptable implemented by the same object as nsiembeddingsitewindow.