Refactor backdrop that is currently used in the maximized mode.

ash/wm/workspace_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_WORKSPACE_CONTROLLER_H_
 #define ASH_WM_WORKSPACE_CONTROLLER_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
 #include "ash/wm/workspace/workspace_types.h"
 #include "base/macros.h"
 #include "ui/aura/window_observer.h"
 
 namespace ash {
 class WorkspaceEventHandler;
 class WorkspaceLayoutManager;
-class WorkspaceLayoutManagerBackdropDelegate;
+class BackdropDelegate;
 
 namespace test {
 class WorkspaceControllerTestApi;
 }
 
 // WorkspaceController acts as a central place that ties together all the
 // various workspace pieces.
 class ASH_EXPORT WorkspaceController : public aura::WindowObserver {
  public:
   // Installs WorkspaceLayoutManager on |viewport|.
   explicit WorkspaceController(aura::Window* viewport);
   ~WorkspaceController() override;
 
   // Returns the current window state.
   wm::WorkspaceWindowState GetWindowState() const;
 
   // Starts the animation that occurs on first login.
   void DoInitialAnimation();
 
   // Add a delegate which adds a backdrop behind the top window of the default
   // workspace.
-  void SetMaximizeBackdropDelegate(
-      std::unique_ptr<WorkspaceLayoutManagerBackdropDelegate> delegate);
+  void SetBackdropDelegate(std::unique_ptr<BackdropDelegate> delegate);
 
   WorkspaceLayoutManager* layout_manager() { return layout_manager_; }
 
  private:
   friend class test::WorkspaceControllerTestApi;
 
   // aura::WindowObserver:
   void OnWindowDestroying(aura::Window* window) override;
 
   aura::Window* viewport_;
   std::unique_ptr<WorkspaceEventHandler> event_handler_;
 
   // Owned by |viewport_|.
   WorkspaceLayoutManager* layout_manager_;
 
   DISALLOW_COPY_AND_ASSIGN(WorkspaceController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_WORKSPACE_CONTROLLER_H_