code below throws "Error during experimental.popup.show: Not an extension view" -

var url = "slide.html"
var showDetails = {"relativeTo": el };
chrome.experimental.popup.show(
url,
showDetails,
function() {alert("experimental.popup.show()");}
);


called from "chrome.tabs.onUpdated.addListener()" when 'changeInfo.status == "complete"'

any ideas?