Remove the OnError method from notification delegates.

chrome/browser/notifications/notification_object_proxy.cc

 // Copyright (c) 2012 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 "chrome/browser/notifications/notification_object_proxy.h"
 
 #include "base/guid.h"
 #include "content/public/browser/desktop_notification_delegate.h"
 
 NotificationObjectProxy::NotificationObjectProxy(
     scoped_ptr<content::DesktopNotificationDelegate> delegate)
     : delegate_(delegate.Pass()),
       displayed_(false),
       id_(base::GenerateGUID()) {}
 
 NotificationObjectProxy::~NotificationObjectProxy() {}
 
 void NotificationObjectProxy::Display() {
   // This method is called each time the notification is shown to the user
   // but we only want to fire the event the first time.
   if (displayed_)
     return;
   displayed_ = true;
 
   delegate_->NotificationDisplayed();
 }
 
-void NotificationObjectProxy::Error() {
-  delegate_->NotificationError();
-}
-
 void NotificationObjectProxy::Close(bool by_user) {
   delegate_->NotificationClosed(by_user);
 }
 
 void NotificationObjectProxy::Click() {
   delegate_->NotificationClick();
 }
 
 std::string NotificationObjectProxy::id() const {
   return id_;
 }