The source code

    /**
     * @class Ext.ux.TabCloseMenu
     * @extends Object
     * Plugin (ptype = 'tabclosemenu') for adding a close context menu to tabs.
     *
     * @ptype tabclosemenu
     */
    Ext.ux.TabCloseMenu = function(){
        var tabs, menu, ctxItem;
        this.init = function(tp){
            tabs = tp;
            tabs.on('contextmenu', onContextMenu);
        };

        function onContextMenu(ts, item, e){
            if(!menu){ // create context menu on first right click
                menu = new Ext.menu.Menu({
                items: [{
                    id: tabs.id + '-close',
                    text: 'Close Tab',
                    handler : function(){
                        tabs.remove(ctxItem);
                    }
                },{
                    id: tabs.id + '-close-others',
                    text: 'Close Other Tabs',
                    handler : function(){
                        tabs.items.each(function(item){
                            if(item.closable && item != ctxItem){
                                tabs.remove(item);
                            }
                        });
                    }
                }]});
            }
            ctxItem = item;
            var items = menu.items;
            items.get(tabs.id + '-close').setDisabled(!item.closable);
            var disableOthers = true;
            tabs.items.each(function(){
                if(this != item && this.closable){
                    disableOthers = false;
                    return false;
                }
            });
            items.get(tabs.id + '-close-others').setDisabled(disableOthers);
    	e.stopEvent();
            menu.showAt(e.getPoint());
        }
    };

    Ext.preg('tabclosemenu', Ext.ux.TabCloseMenu);