// Called when the url of a tab changes.
// So we can notify users
    var notification = webkitNotifications.createNotification(
    '48.png',
    'Alert!'
);
      // Called when the url of a tab changes.
      function checkForValidUrl(tab) {
        // Compare with a the URL
        if (tab.url.match(/google/)) {
          //then
          notification.show();
        }
      };
  // Listen for any changes to the URL of any tab.
chrome.tabs.onUpdated.addListener(function(tabId, changeInfo, tab){
    if(changeInfo.status == "loading") {
        checkForValidUrl(tab);
    }
});

chrome.tabs.onSelectionChanged.addListener(function(tabId, selectInfo){
    chrome.tabs.getSelected(null, function(tab){
        checkForValidUrl(tab);
    });
});

function checkForValidUrl(tabId, changeInfo, tab) {

var notification = webkitNotifications.createNotification(
'48.png',
'Alert!',
'Watch out for your privacy!'
);

// Compare with the URL
if (tab.url.match(/google/)) {
    //then
notification.show();
}
};

chrome.tabs.onUpdated.addListener(function(tabId, changeInfo, tab){
    if(changeInfo.status == "loading") {
        checkForValidUrl(tabId, changeInfo, tab);
    }
});