Use container::back() and container::pop_back() in ui/

ui/message_center/notification_list_unittest.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 "ui/message_center/notification_list.h"
 
 #include <stddef.h>
 
 #include <utility>
 
@@ skipping 277 matching lines @@
   for (size_t i = 0; i < kMaxVisiblePopupNotifications; ++i, ++iter) {
     EXPECT_EQ(ids[i], (*iter)->id()) << i;
   }
 
   for (NotificationList::PopupNotifications::const_iterator iter =
            popups.begin(); iter != popups.end(); ++iter) {
     notification_list()->MarkSinglePopupAsShown((*iter)->id(), false);
   }
   popups.clear();
   popups = GetPopups();
-  EXPECT_EQ(1u, popups.size());
-  EXPECT_EQ(ids[ids.size() - 1], (*popups.begin())->id());
+  ASSERT_EQ(1u, popups.size());
+  EXPECT_EQ(ids.back(), (*popups.begin())->id());
 }
 
 TEST_F(NotificationListTest, Priority) {
   ASSERT_EQ(0u, notification_list()->NotificationCount(blockers()));
   ASSERT_EQ(0u, notification_list()->UnreadCount(blockers()));
 
   // Default priority has the limit on the number of the popups.
   for (size_t i = 0; i <= kMaxVisiblePopupNotifications; ++i)
     AddNotification();
   EXPECT_EQ(kMaxVisiblePopupNotifications + 1,
@@ skipping 352 matching lines @@
       NotifierId(), RichNotificationData(), NULL));
   notification_list()->AddNotification(std::move(updated_notification));
 
   EXPECT_FALSE(notification_list()->HasNotificationOfType(
       id, message_center::NOTIFICATION_TYPE_SIMPLE));
   EXPECT_TRUE(notification_list()->HasNotificationOfType(
       id, message_center::NOTIFICATION_TYPE_PROGRESS));
 }
 
 }  // namespace message_center