Moves a couple of the maximize mode classes to ash/common

ash/wm/maximize_mode/workspace_backdrop_delegate.h

 // Copyright 2014 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_MAXIMIZE_MODE_WORKSPACE_BACKDROP_DELEGATE_H_
 #define ASH_WM_MAXIMIZE_MODE_WORKSPACE_BACKDROP_DELEGATE_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
 #include "ash/common/wm/workspace/workspace_layout_manager_backdrop_delegate.h"
-#include "base/compiler_specific.h"
 #include "base/macros.h"
 
-namespace aura {
-class Window;
-}
-
 namespace views {
 class Widget;
 }
 
 namespace ash {
 
+class WmWindow;
+
 // A background which gets created for a container |window| and which gets
 // stacked behind the topmost window (within that container) covering the
 // entire container.
 class ASH_EXPORT WorkspaceBackdropDelegate
     : public WorkspaceLayoutManagerBackdropDelegate {
  public:
-  explicit WorkspaceBackdropDelegate(aura::Window* container);
+  explicit WorkspaceBackdropDelegate(WmWindow* container);
   ~WorkspaceBackdropDelegate() override;
 
   // WorkspaceLayoutManagerBackdropDelegate overrides:
   void OnWindowAddedToLayout(WmWindow* child) override;
   void OnWindowRemovedFromLayout(WmWindow* child) override;
   void OnChildWindowVisibilityChanged(WmWindow* child, bool visible) override;
   void OnWindowStackingChanged(WmWindow* window) override;
   void OnPostWindowStateTypeChange(wm::WindowState* window_state,
                                    wm::WindowStateType old_type) override;
   void OnDisplayWorkAreaInsetsChanged() override;
 
  private:
   class WindowObserverImpl;
 
   // Restack the backdrop relatively to the other windows in the container.
   void RestackBackdrop();
 
   // Returns the current visible top level window in the container.
-  aura::Window* GetCurrentTopWindow();
+  WmWindow* GetCurrentTopWindow();
 
   // Position & size the background over the container window.
   void AdjustToContainerBounds();
 
   // Show the overlay.
   void Show();
 
   std::unique_ptr<WindowObserverImpl> container_observer_;
 
   // The background which covers the rest of the screen.
-  views::Widget* background_;
+  views::Widget* background_ = nullptr;
+  // WmWindow for |background_|.
+  WmWindow* background_window_ = nullptr;
 
   // The window which is being "maximized".
-  aura::Window* container_;
+  WmWindow* container_;
 
   // If true, the |RestackOrHideWindow| might recurse.
   bool in_restacking_;
 
   DISALLOW_COPY_AND_ASSIGN(WorkspaceBackdropDelegate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_MAXIMIZE_MODE_WORKSPACE_BACKDROP_DELEGATE_H_