Bug 1483153 - Let menulist popups inherit the font from their menulist parent. r=felipe

toolkit/themes/linux/global/menu.css

@@ -80,7 +80,7 @@ menucaption {
 /* ::::: menu/menuitems in menulist popups ::::: */
 
 menulist > menupopup {
-  font: message-box;
+  font: inherit;
 }
 
 menulist > menupopup > menuitem,

toolkit/themes/windows/global/menu.css

@@ -170,7 +170,7 @@ menuitem[_moz-menuactive="true"] {
 /* ::::: menu/menuitems in menulist popups ::::: */
 
 menulist > menupopup {
-  font: message-box;
+  font: inherit;
 }
 
 menulist > menupopup > menuitem,