I want to add tooltip when Tab panel property set to

closable:true

Here is my code
===========================
//Override the Panel gettool() method

Ext.override(Ext.Panel, {

// Returns tool object with specified id
getTool: function(id) {
if (Ext.isArray(this.tools)) {
for (var i = 0; i < this.tools.length; i++) {
if (this.tools[i].id == id) {
return this.tools[i];
}
}
} else if (Ext.isObject(this.tools)) {
return this.tools[id];
}
}


});

==============================================

//Create a tab Panel
TabPanel = Ext.extend(Ext.Panel, {

initComponent: function() {
TabPanel.superclass.initComponent.call(this);
},
initTools: function(){
TabPanel.superclass.initTools.call(this);
// Set qtip for the close tool that was just added
this.getTool('close').set({qtip:'Close'});
}

});

Ext.reg('TabPanel', TabPanel);

================
Instantiate TabPanel

var addNewTab = function(oUri, oParams, oTitle, oTabID) {
var oPanel = Ext.getCmp('maintab');
var tabItem;

var itemPresent = oPanel.items.length;

tabItem = new TabPanel({
id: 'tab_' + oTabID,
title: oTitle,
tabtip: oTitle,
iconCls: 'tabs',
layout: 'fit',
autoScroll: true,
closable: true
});


//Add tab to panel
if (oTabID === 'OrderDtlId') {
if(Ext.getCmp('tab_35011')){
// always add order details next to orders panel
oPanel.insert(oPanel.items.indexOf(Ext.getCmp('tab_35011'))+1,tabItem);
} else {
oPanel.add(tabItem);
}
}
else {
oPanel.add(tabItem);
}
oPanel.doLayout();
Ext.getCmp('tab_' + oTabID).show();
}
}
===================================

How to add tool tip for panel collapsable icon '>>' this icon