--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -5820,42 +5820,99 @@ var IndexedDBPromptHelper = {
       responseTopic = this._permissionsResponse;
     }
     else if (topic == this._quotaPrompt) {
       message = gNavigatorBundle.getFormattedString("indexedDB.usage",
                                                     [ host, data ]);
       responseTopic = this._quotaResponse;
     }
 
-    var self = this;
+    const hiddenTimeoutDuration = 30000; // 30 seconds
+    const firstTimeoutDuration = 120000; // 2 minutes
+
+    var timeoutId;
+
+    function cleanup() {
+      if (timeoutId) {
+        clearTimeout(timeoutId);
+        delete timeoutId;
+      }
+    }
+
     var observer = requestor.getInterface(Ci.nsIObserver);
 
     var mainAction = {
       label: gNavigatorBundle.getString("offlineApps.allow"),
       accessKey: gNavigatorBundle.getString("offlineApps.allowAccessKey"),
       callback: function() {
+        cleanup();
         observer.observe(null, responseTopic,
                          Ci.nsIPermissionManager.ALLOW_ACTION);
       }
     };
 
     var secondaryActions = [
       {
         label: gNavigatorBundle.getString("offlineApps.never"),
         accessKey: gNavigatorBundle.getString("offlineApps.neverAccessKey"),
         callback: function() {
+          cleanup();
           observer.observe(null, responseTopic,
                            Ci.nsIPermissionManager.DENY_ACTION);
         }
       }
     ];
 
-    PopupNotifications.show(browser, topic, message, this._notificationIcon,
-                            mainAction, secondaryActions);
-
+    // This will be set to the result of PopupNotifications.show() below.
+    var notification;
+
+    function timeoutNotification() {
+      // Remove the notification.
+      notification.remove();
+
+      // Clear all of our timeout stuff.
+      cleanup();
+
+      // And tell the page that the popup timed out.
+      observer.observe(null, responseTopic,
+                       Ci.nsIPermissionManager.UNKNOWN_ACTION);
+    }
+
+    var options = {
+      eventCallback: function(state) {
+        // Don't do anything if the timeout has not been set or if a selection
+        // has already been made (either by user action or by timing out).
+        if (!timeoutId) {
+          return;
+        }
+
+        // If the popup is being dismissed start the short timeout.
+        if (state == "dismissed") {
+          clearTimeout(timeoutId);
+          timeoutId = setTimeout(timeoutNotification, hiddenTimeoutDuration);
+          return;
+        }
+
+        // If the popup is being re-shown then clear the timeout allowing
+        // unlimited waiting. Don't unset timeoutId though or we will fail to
+        // launch the short timeout if the popup is dismissed.
+        else if (state == "shown") {
+          clearTimeout(timeoutId);
+        }
+      }
+    };
+
+    notification = PopupNotifications.show(browser, topic, message,
+                                           this._notificationIcon, mainAction,
+                                           secondaryActions, options);
+
+    // Set the timeoutId after the popup has been created, and use the long
+    // timeout value. If the user doesn't notice the popup after this amount of
+    // time then it is most likely not visible and we want to alert the page.
+    timeoutId = setTimeout(timeoutNotification, firstTimeoutDuration);
   }
 };
 
 function WindowIsClosing()
 {
   if (TabView.isVisible()) {
     TabView.hide();
     return false;