Bug 1079303 - part 2: fix tests to not expect sync behaviour from notification.reshow, r=dolske

browser/base/content/test/plugins/head.js

@@ -153,6 +153,26 @@ function waitForNotificationBar(notificationID, browser, callback) {
   });
 }
 
+/**
+ * Reshow a notification and call a callback when it is reshown.
+ * @param notification
+ *        The notification to reshow
+ * @param callback
+ *        A function to be called when the notification has been reshown
+ */
+function waitForNotificationShown(notification, callback)
+{
+  if (PopupNotifications.panel.state == "open") {
+    executeSoon(callback);
+    return;
+  }
+  PopupNotifications.panel.addEventListener("popupshown", function onShown(e) {
+    PopupNotifications.panel.removeEventListener("popupshown", onShown);
+    callback();
+  }, false);
+  notification.reshow();
+}
+
 /**
  * Due to layout being async, "PluginBindAttached" may trigger later.
  * This returns a Promise that resolves once we've forced a layout