Replaces existing tabs with a new set. If there were more tabs before, the additional ones are not removed. You can use the removeTab method to remove the existing tabs first if that is desired. The argument should be an array of objects, one for each document to load. The objects may be defined in script and contain a URI property for the URL of the page to load. A referrerURI property may also be optionally used to set the referrer page. This method returns an array of the session history objects for the tabs that were removed.