Add presubmit check for scoped_ptr usage.

ui/message_center/message_center_impl.cc

 // Copyright (c) 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/message_center_impl.h"
 
 #include <algorithm>
 
 #include "base/memory/scoped_vector.h"
 #include "base/observer_list.h"
@@ skipping 177 matching lines @@
 
 void ChangeQueue::UpdateNotification(const std::string& old_id,
                                      scoped_ptr<Notification> notification) {
   std::string new_id = notification->id();
   scoped_ptr<Change> change(
       new Change(CHANGE_TYPE_UPDATE, new_id, notification.Pass()));
   Replace(old_id, change.Pass());
 }
 
 void ChangeQueue::EraseNotification(const std::string& id, bool by_user) {
-  scoped_ptr<Change> change(
-      new Change(CHANGE_TYPE_DELETE, id, scoped_ptr<Notification>()));
+  scoped_ptr<Change> change(new Change(CHANGE_TYPE_DELETE, id, nullptr));
   change->set_by_user(by_user);
   Replace(id, change.Pass());
 }
 
 bool ChangeQueue::Has(const std::string& id) const {
   ScopedVector<Change>::const_iterator iter =
       std::find_if(changes_.begin(), changes_.end(), ChangeFinder(id));
   return iter != changes_.end();
 }
 
@@ skipping 668 matching lines @@
 void MessageCenterImpl::PausePopupTimers() {
   if (popup_timers_controller_)
     popup_timers_controller_->PauseAll();
 }
 
 void MessageCenterImpl::DisableTimersForTest() {
   popup_timers_controller_.reset();
 }
 
 }  // namespace message_center