Notifications: fix TODO in notification_database.cc.

Change-Id: If9bd995760570480c0ab0c13de09e6e84d07a8fa
Reviewed-on: https://chromium-review.googlesource.com/1098687Reviewed-by: Peter Beverloo <peter@chromium.org>
Commit-Queue: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#566972}

content/browser/notifications/notification_database.cc

@@ -424,11 +424,7 @@ NotificationDatabase::DeleteAllNotificationDataInternal(
 
     batch.Delete(iter->key());
 
-    // Silently remove the notification if it doesn't have an ID assigned.
-    // TODO(peter): Remove this clause when Chrome 55 has branched.
-    if (notification_database_data.notification_id.empty())
-      continue;
-
+    DCHECK(!notification_database_data.notification_id.empty());
     deleted_notification_ids->insert(
         notification_database_data.notification_id);
   }