Use notification display service to collect persistent notifications.

chrome/test/data/notifications/platform_notification_service.html

Index: chrome/test/data/notifications/platform_notification_service.html
diff --git a/chrome/test/data/notifications/platform_notification_service.html b/chrome/test/data/notifications/platform_notification_service.html
index 88b2ac3e4c5f1cfe8c41ee8be80bf3ac7688ba7d..4be95161f173df973dc6da1fffd564aae6e32602 100644
--- a/chrome/test/data/notifications/platform_notification_service.html
+++ b/chrome/test/data/notifications/platform_notification_service.html
@@ -21,6 +21,14 @@
         });
       }
 
+      function DisplayNonPersistentNotification(title, options) {
+        const notification = new Notification(title, options || {});
+        notification.addEventListener('show', e =>
+          domAutomationController.send('ok'));
+        notification.addEventListener('error', e =>
+          domAutomationController.send('could not show notification'));
+      }
+
       // Renews the registered Service Worker registration for this page, then
       // displays a notification on the activated ServiceWorkerRegistration.
       function DisplayPersistentNotification(title, options) {
@@ -127,6 +135,29 @@
         });
       }
 
+      // Gets a comma separated list of currently displayed notification titles
+      function GetDisplayedNotifications() {
+        GetActivatedServiceWorker('platform_notification_service.js',
+          location.pathname).then(function (sw) {
+            return sw.getNotifications();
+          }).then(function (notifications) {
+            var notificationResult = '';
+              for (var i = 0; i < notifications.length; ++i) {
+                notificationResult = notificationResult.concat(notifications[i].title);
+                  if (i < (notifications.length -1))
+                    notificationResult = notificationResult.concat(',');
+              }
+              if (expectingMessage)
+                domAutomationController.send(notificationResult);
+              else
+                messageStack.push(notificationResult);

[Peter Beverloo, 2016/12/06 13:04:02]

micro nit: -2 space indent for lines 146-153

[Miguel Garcia, 2016/12/07 17:20:50]

Done.

+
+            domAutomationController.send('ok');
+          }).catch(function (error) {
+            domAutomationController.send('' + error);
+          });
+      }
+
       // Returns the latest received message from the worker. If no message has
       // been received, nothing will be done. For successfully registered
       // Service Workers this is OK, however, since the "message" event handler