lib/Ext/tab/Panel.js
function(tabBar, newTab) {
        var oldActiveItem = this.getActiveItem(),
            newActiveItem;

        this.setActiveItem(tabBar.indexOf(newTab));
        newActiveItem = this.getActiveItem();
        return this.forcedChange || oldActiveItem !== newActiveItem;
    }
function(tabBar, newTab) {
        var oldActiveItem = this.getActiveItem(),
            newActiveItem;

        this.setActiveItem(tabBar.indexOf(newTab));
        newActiveItem = this.getActiveItem();
        return this.forcedChange || oldActiveItem !== newActiveItem;
    }
Updates this container with the new active item.
@param {Object} tabBar
@param {Object} newTab
@return {Boolean}