Remove the OnError method from notification delegates.

ui/message_center/notification_delegate.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/message_center/notification_delegate.h"
 
 namespace message_center {
 
 // NotificationDelegate:
 
 bool NotificationDelegate::HasClickedListener() { return false; }
 
 void NotificationDelegate::ButtonClick(int button_index) {}
 
 // HandleNotificationClickedDelegate:
 
 HandleNotificationClickedDelegate::HandleNotificationClickedDelegate(
     const base::Closure& closure)
     : closure_(closure) {
 }
 
 HandleNotificationClickedDelegate::~HandleNotificationClickedDelegate() {
 }
 
 void HandleNotificationClickedDelegate::Display() {
 }
 
-void HandleNotificationClickedDelegate::Error() {
-}
-
 void HandleNotificationClickedDelegate::Close(bool by_user) {
 }
 
 bool HandleNotificationClickedDelegate::HasClickedListener() {
   return !closure_.is_null();
 }
 
 void HandleNotificationClickedDelegate::Click() {
   if (!closure_.is_null())
     closure_.Run();
 }
 
 void HandleNotificationClickedDelegate::ButtonClick(int button_index) {
 }
 
 // HandleNotificationButtonClickDelegate:
 
 HandleNotificationButtonClickDelegate::HandleNotificationButtonClickDelegate(
     const ButtonClickCallback& button_callback)
     : button_callback_(button_callback) {
 }
 
 HandleNotificationButtonClickDelegate::
     ~HandleNotificationButtonClickDelegate() {
 }
 
 void HandleNotificationButtonClickDelegate::Display() {
 }
 
-void HandleNotificationButtonClickDelegate::Error() {
-}
-
 void HandleNotificationButtonClickDelegate::Close(bool by_user) {
 }
 
 void HandleNotificationButtonClickDelegate::Click() {
 }
 
 void HandleNotificationButtonClickDelegate::ButtonClick(int button_index) {
   if (!button_callback_.is_null())
     button_callback_.Run(button_index);
 }
 
 }  // namespace message_center