Use notification display service to collect persistent notifications.

chrome/browser/notifications/platform_notification_service_impl.cc

Index: chrome/browser/notifications/platform_notification_service_impl.cc
diff --git a/chrome/browser/notifications/platform_notification_service_impl.cc b/chrome/browser/notifications/platform_notification_service_impl.cc
index 2f79b35ba28726a7a4df6c89f2a6657713a91913..1562b95f04994f887cb3c79e52a6bbfcad2fed0c 100644
--- a/chrome/browser/notifications/platform_notification_service_impl.cc
+++ b/chrome/browser/notifications/platform_notification_service_impl.cc
@@ -31,6 +31,7 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/desktop_notification_delegate.h"
 #include "content/public/browser/notification_event_dispatcher.h"
+#include "content/public/browser/notification_id_verifier.h"
 #include "content/public/browser/permission_type.h"
 #include "content/public/browser/user_metrics.h"
 #include "content/public/common/notification_resources.h"
@@ -370,9 +371,20 @@ bool PlatformNotificationServiceImpl::GetDisplayedPersistentNotifications(
   if (!profile || profile->AsTestingProfile())
     return false;  // Tests will not have a message center.
 
-  // TODO(peter): Filter for persistent notifications only.
-  return GetNotificationDisplayService(profile)->GetDisplayed(
-      displayed_notifications);
+  // Filter out non persistent notifications.
+  if (GetNotificationDisplayService(profile)->GetDisplayed(
+          displayed_notifications)) {
+    for (auto it = displayed_notifications->begin();
+         it != displayed_notifications->end();) {
+      if (content::NotificationIdVerifier::IsNonPersistentNotification(*it)) {
+        it = displayed_notifications->erase(it);
+      } else {
+        ++it;
+      }
+    }
+    return true;
+  }
+  return false;
 }
 
 void PlatformNotificationServiceImpl::OnClickEventDispatchComplete(