Remove the OnError method from notification delegates.

chrome/browser/chromeos/net/network_portal_notification_controller.cc

Index: chrome/browser/chromeos/net/network_portal_notification_controller.cc
diff --git a/chrome/browser/chromeos/net/network_portal_notification_controller.cc b/chrome/browser/chromeos/net/network_portal_notification_controller.cc
index 897511fc6d0c0edb5c5878ebd4fa1b283228e828..17ad3559ba1da68cc749bb1557051dd739856ecd 100644
--- a/chrome/browser/chromeos/net/network_portal_notification_controller.cc
+++ b/chrome/browser/chromeos/net/network_portal_notification_controller.cc
@@ -55,7 +55,6 @@ class NetworkPortalNotificationControllerDelegate
 
   // Overridden from message_center::NotificationDelegate:
   virtual void Display() override;
-  virtual void Error() override;
   virtual void Close(bool by_user) override;
   virtual void Click() override;
 
@@ -74,13 +73,6 @@ void NetworkPortalNotificationControllerDelegate::Display() {
       NetworkPortalNotificationController::NOTIFICATION_METRIC_COUNT);
 }
 
-void NetworkPortalNotificationControllerDelegate::Error() {
-  UMA_HISTOGRAM_ENUMERATION(
-      NetworkPortalNotificationController::kNotificationMetric,
-      NetworkPortalNotificationController::NOTIFICATION_METRIC_ERROR,
-      NetworkPortalNotificationController::NOTIFICATION_METRIC_COUNT);
-}
-
 void NetworkPortalNotificationControllerDelegate::Close(bool by_user) {
   if (clicked_)
     return;