Use container::back() and container::pop_back().

ash/display/mirror_window_controller.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 "ash/display/mirror_window_controller.h"
 
 #include <utility>
 
 #if defined(USE_X11)
 #include <X11/extensions/XInput2.h>
@@ skipping 252 matching lines @@
         CloseAndDeleteHost(iter->second, true);
         iter = mirroring_host_info_map_.erase(iter);
       } else {
         ++iter;
       }
     }
   }
 }
 
 void MirrorWindowController::UpdateWindow() {
-  if (!mirroring_host_info_map_.size())
+  if (mirroring_host_info_map_.empty())
     return;
   DisplayManager* display_manager = Shell::GetInstance()->display_manager();
   std::vector<DisplayInfo> display_info_list;
   for (auto& pair : mirroring_host_info_map_)
     display_info_list.push_back(display_manager->GetDisplayInfo(pair.first));
   UpdateWindow(display_info_list);
 }
 
 void MirrorWindowController::CloseIfNotNecessary() {
   DisplayManager::MultiDisplayMode new_mode = GetCurrentMultiDisplayMode();
@@ skipping 96 matching lines @@
   // EventProcessor may be accessed after this call if the mirroring window
   // was deleted as a result of input event (e.g. shortcut), so don't delete
   // now.
   if (delay_host_deletion)
     base::ThreadTaskRunnerHandle::Get()->DeleteSoon(FROM_HERE, host_info);
   else
     delete host_info;
 }
 
 }  // namespace ash