Create a LayerDelegate for recreated layers to draw when their content is invalidated.

ash/wm/drag_window_controller.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_DRAG_WINDOW_CONTROLLER_H_
 #define ASH_WM_DRAG_WINDOW_CONTROLLER_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 23 matching lines @@
 
   explicit DragWindowController(aura::Window* window);
   virtual ~DragWindowController();
 
   // This is used to update the bounds and opacity for the drag window
   // immediately.
   // This also creates/destorys the drag window when necessary.
   void Update(const gfx::Rect& bounds_in_screen,
               const gfx::Point& drag_location_in_screen);
 
+ private:
+  class DragWindowDetails;
+  FRIEND_TEST_ALL_PREFIXES(DragWindowResizerTest, DragWindowController);
+  FRIEND_TEST_ALL_PREFIXES(DragWindowResizerTest,
+                           DragWindowControllerAcrossThreeDisplays);
+
   // Returns the currently active drag windows.
   int GetDragWindowsCountForTest() const;
 
   // Returns the drag window/layer owner for given index of the
   // currently active drag windows list.
   const aura::Window* GetDragWindowForTest(size_t index) const;
   const ui::LayerTreeOwner* GetDragLayerOwnerForTest(size_t index) const;
 
- private:
-  class DragWindowDetails;
+  // Call Layer::OnPaintLayer on all layers under the drag_windows_.
+  void RequestLayerPaintForTest();
 
   // Window the drag window is placed beneath.
   aura::Window* window_;
 
   std::vector<std::unique_ptr<DragWindowDetails>> drag_windows_;
 
   DISALLOW_COPY_AND_ASSIGN(DragWindowController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_DRAG_WINDOW_CONTROLLER_H_