Refactors DimWindow and moves to ash/common

ash/wm/system_modal_container_layout_manager.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_WM_SYSTEM_MODAL_CONTAINER_LAYOUT_MANAGER_H_
 #define ASH_WM_SYSTEM_MODAL_CONTAINER_LAYOUT_MANAGER_H_
 
 #include <vector>
 
 #include "ash/ash_export.h"
 #include "ash/snap_to_pixel_layout_manager.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "ui/aura/window_observer.h"
 #include "ui/keyboard/keyboard_controller_observer.h"
 
 namespace aura {
 class Window;
 class EventFilter;
 }
 namespace gfx {
 class Rect;
 }
 
 namespace ash {
-class DimWindow;
+class WindowDimmer;
 
 // LayoutManager for the modal window container.
 // System modal windows which are centered on the screen will be kept centered
 // when the container size changes.
 class ASH_EXPORT SystemModalContainerLayoutManager
     : public SnapToPixelLayoutManager,
       public aura::WindowObserver,
       public keyboard::KeyboardControllerObserver {
  public:
   explicit SystemModalContainerLayoutManager(aura::Window* container);
   ~SystemModalContainerLayoutManager() override;
 
-  bool has_modal_background() const { return modal_background_ != NULL; }
+  bool has_window_dimmer() const { return window_dimmer_ != nullptr; }
 
   // Overridden from SnapToPixelLayoutManager:
   void OnWindowResized() override;
   void OnWindowAddedToLayout(aura::Window* child) override;
   void OnWillRemoveWindowFromLayout(aura::Window* child) override;
   void SetChildBounds(aura::Window* child,
                       const gfx::Rect& requested_bounds) override;
 
   // Overridden from aura::WindowObserver:
   void OnWindowPropertyChanged(aura::Window* window,
@@ skipping 40 matching lines @@
   // Returns true if |window_bounds| is centered.
   bool DialogIsCentered(const gfx::Rect& window_bounds);
 
   aura::Window* modal_window() {
     return !modal_windows_.empty() ? modal_windows_.back() : NULL;
   }
 
   // The container that owns the layout manager.
   aura::Window* container_;
 
-  // A window that dims the windows behind the modal window(s) being
-  // shown in |container_|.
-  DimWindow* modal_background_;
+  // WindowDimmer used to dim windows behind the modal window(s) being shown in
+  // |container_|.
+  WindowDimmer* window_dimmer_ = nullptr;
 
   // A stack of modal windows. Only the topmost can receive events.
   std::vector<aura::Window*> modal_windows_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemModalContainerLayoutManager);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_SYSTEM_MODAL_CONTAINER_LAYOUT_MANAGER_H_