Remove the OnError method from notification delegates.

ash/system/chromeos/screen_security/screen_tray_item.h

 // 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.
 
 #ifndef ASH_SYSTEM_CHROMEOS_SCREEN_TRAY_ITEM_H_
 #define ASH_SYSTEM_CHROMEOS_SCREEN_TRAY_ITEM_H_
 
 #include "ash/system/tray/system_tray.h"
 #include "ash/system/tray/system_tray_item.h"
 #include "ash/system/tray/system_tray_notifier.h"
@@ skipping 56 matching lines @@
 
   DISALLOW_COPY_AND_ASSIGN(ScreenStatusView);
 };
 
 class ScreenNotificationDelegate : public message_center::NotificationDelegate {
  public:
   explicit ScreenNotificationDelegate(ScreenTrayItem* screen_tray);
 
   // message_center::NotificationDelegate overrides:
   virtual void Display() override;
-  virtual void Error() override;
   virtual void Close(bool by_user) override;
   virtual void Click() override;
   virtual void ButtonClick(int button_index) override;
 
  protected:
   virtual ~ScreenNotificationDelegate();
 
  private:
   ScreenTrayItem* screen_tray_;
 
@@ skipping 47 matching lines @@
   tray::ScreenStatusView* default_view_;
   bool is_started_;
   base::Closure stop_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(ScreenTrayItem);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_SCREEN_TRAY_ITEM_H_