Adding UMA for persistent notifications.

content/public/common/persistent_notification_status.h

Index: content/public/common/persistent_notification_status.h
diff --git a/content/public/common/persistent_notification_status.h b/content/public/common/persistent_notification_status.h
index b8f14094b3a5203e5c355cad5b66be397adf22ee..82c5240e83d3805996cb4d2a9b117ae68642af5c 100644
--- a/content/public/common/persistent_notification_status.h
+++ b/content/public/common/persistent_notification_status.h
@@ -8,6 +8,7 @@
 namespace content {
 
 // Delivery status for persistent notification clicks to a Service Worker.
+// NotificationStatus entries should not be reordered or removed.

[Peter Beverloo, 2015/05/27 12:28:48]

nit: Either "PersistentNotificationStatus entries should..." or just "Entries
should..."

[Deepak, 2015/05/27 12:42:38]

Done.

 enum PersistentNotificationStatus {
   // The notificationclick event has been delivered successfully.
   PERSISTENT_NOTIFICATION_STATUS_SUCCESS = 0,
@@ -25,6 +26,8 @@ enum PersistentNotificationStatus {
   // The event could not be delivered because the data associated with the
   // notification could not be read from the database.
   PERSISTENT_NOTIFICATION_STATUS_DATABASE_ERROR,
+
+  PERSISTENT_NOTIFICATION_STATUS_MAX

[Peter Beverloo, 2015/05/27 12:28:48]

nit: Please add a comment above this line saying:

// Only add new entries above this line.

[Deepak, 2015/05/27 12:42:38]

Done.

 };
 
 }  // content