Remove some ifdefs from ash since it only supports ChromeOS now.

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 182 matching lines @@
       InitRootWindowSettings(host->window())->display_id = display_info.id();
       host->InitHost();
       host->window()->Show();
 #if defined(USE_X11)
       if (!display_manager->IsInUnifiedMode()) {
         // Mirror window shouldn't handle input events.
         static_cast<aura::WindowTreeHostX11*>(host)->DisableInput();
       }
 #endif
 
-#if defined(OS_CHROMEOS)
       if (display_manager->IsInUnifiedMode()) {
         host_info->ash_host->ConfineCursorToRootWindow();
         AshWindowTreeHost* unified_ash_host =
             Shell::GetInstance()
                 ->window_tree_host_manager()
                 ->GetAshWindowTreeHostForDisplayId(
                     display::Screen::GetScreen()->GetPrimaryDisplay().id());
         unified_ash_host->RegisterMirroringHost(host_info->ash_host.get());
         aura::client::SetScreenPositionClient(host->window(),
                                               screen_position_client_.get());
       }
-#endif
 
       aura::client::SetCaptureClient(host->window(), new NoneCaptureClient());
       host->Show();
 
       aura::Window* mirror_window = host_info->mirror_window =
           new aura::Window(nullptr);
       mirror_window->Init(ui::LAYER_SOLID_COLOR);
       host->window()->AddChild(mirror_window);
       host_info->ash_host->SetRootWindowTransformer(std::move(transformer));
       mirror_window->SetBounds(host->window()->bounds());
@@ skipping 148 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