Add presubmit check for scoped_ptr usage.

ui/message_center/views/message_center_view_unittest.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 <map>
 
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/strings/utf_string_conversions.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 174 matching lines @@
     bool by_user) {
   // For this test, this method should not be invoked.
   NOTREACHED();
 }
 
 scoped_ptr<ui::MenuModel> MessageCenterViewTest::CreateMenuModel(
     const NotifierId& notifier_id,
     const base::string16& display_source) {
   // For this test, this method should not be invoked.
   NOTREACHED();
-  return scoped_ptr<ui::MenuModel>();
+  return nullptr;
 }
 
 bool MessageCenterViewTest::HasClickedListener(
     const std::string& notification_id) {
   return true;
 }
 
 void MessageCenterViewTest::ClickOnNotificationButton(
     const std::string& notification_id,
     int button_index) {
@@ skipping 27 matching lines @@
   // GetHeightForWidth() calls per descendant NotificationView. 20 is a very
   // large number corresponding to the current reality. That number will be
   // ratcheted down over time as the code improves.
   EXPECT_LE(GetCallCount(LAYOUT), GetNotificationCount() * 2);
   EXPECT_LE(GetCallCount(GET_PREFERRED_SIZE) +
             GetCallCount(GET_HEIGHT_FOR_WIDTH),
             GetNotificationCount() * 20);
 }
 
 }  // namespace message_center