Clean up most of the ChromeOS headers in non-ChromeOS build

ash/shell.h

 // 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.
 
 #ifndef ASH_SHELL_H_
 #define ASH_SHELL_H_
 
 #include <memory>
 #include <utility>
 #include <vector>
 
 #include "ash/ash_export.h"
 #include "ash/metrics/user_metrics_recorder.h"
 #include "ash/public/cpp/shelf_types.h"
 #include "ash/session/session_observer.h"
-#include "ash/wm/cursor_manager_chromeos.h"
 #include "ash/wm/system_modal_container_event_filter_delegate.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "ui/aura/window.h"
 #include "ui/display/screen.h"
 #include "ui/events/event_target.h"
 #include "ui/wm/core/cursor_manager.h"
 #include "ui/wm/public/activation_change_observer.h"
 
+#if defined(OS_CHROMEOS)
+#include "ash/wm/cursor_manager_chromeos.h"
+#endif  // defined(OS_CHROMEOS)
+
 class PrefService;
 
 namespace aura {
 class RootWindow;
 class UserActivityForwarder;
 class Window;
 class WindowManagerClient;
 class WindowTreeClient;
 namespace client {
 class ActivationClient;
@@ skipping 771 matching lines @@
   base::ObserverList<ShellObserver> shell_observers_;
 
   scoped_refptr<base::SequencedWorkerPool> blocking_pool_;
 
   DISALLOW_COPY_AND_ASSIGN(Shell);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_H_