@-moz-document url("chrome://browser/content/browser.xul") {

#cfx-control-button menupopup,
#cfx-tools-button menupopup {
direction: rtl !important;
-moz-transform: scaleX(-1);
}

#cfx-control-button menupopup menuitem,
#cfx-control-button menupopup menu,
#cfx-tools-button menupopup menuitem,
#cfx-tools-button menupopup menu {
direction: ltr !important;
-moz-transform: scaleX(-1);
}

}