Adding a gray semi transparent backdrop behind the topmost window within the default container

ash/wm/workspace/workspace_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_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_H_
 #define ASH_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_H_
 
 #include <set>
 
 #include "ash/ash_export.h"
 #include "ash/shell_observer.h"
 #include "ash/wm/window_state_observer.h"
 #include "ash/wm/wm_types.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/memory/scoped_ptr.h"
 #include "ui/aura/client/activation_change_observer.h"
 #include "ui/aura/layout_manager.h"
 #include "ui/aura/window_observer.h"
 #include "ui/gfx/rect.h"
 
 namespace aura {
 class RootWindow;
 class Window;
 }
 
 namespace ui {
 class Layer;
 }
 
 namespace ash {
 namespace wm {
 class WindowState;
 class WMEvent;
 }
 
 namespace internal {
 
 class ShelfLayoutManager;
+class WorkspaceLayoutManagerDelegate;
 
 // LayoutManager used on the window created for a workspace.
 class ASH_EXPORT WorkspaceLayoutManager
     : public aura::LayoutManager,
       public aura::WindowObserver,
       public aura::client::ActivationChangeObserver,
       public ShellObserver,
       public wm::WindowStateObserver {
  public:
   explicit WorkspaceLayoutManager(aura::Window* window);
   virtual ~WorkspaceLayoutManager();
 
   void SetShelf(internal::ShelfLayoutManager* shelf);
 
+  // A delegate which can be set to add a backdrop behind the top most visible
+  // window. With the call the ownership of the delegate will be transferred to
+  // the WorkspaceLayoutManager.
+  void SetMaximizeBackdropDelegate(
+      scoped_ptr<WorkspaceLayoutManagerDelegate> delegate);
+
   // Overridden from aura::LayoutManager:
   virtual void OnWindowResized() OVERRIDE {}
   virtual void OnWindowAddedToLayout(aura::Window* child) OVERRIDE;
   virtual void OnWillRemoveWindowFromLayout(aura::Window* child) OVERRIDE;
   virtual void OnWindowRemovedFromLayout(aura::Window* child) OVERRIDE;
   virtual void OnChildWindowVisibilityChanged(aura::Window* child,
                                               bool visibile) OVERRIDE;
   virtual void SetChildBounds(aura::Window* child,
                               const gfx::Rect& requested_bounds) OVERRIDE;
 
@@ skipping 58 matching lines @@
 
   // Set of windows we're listening to.
   WindowSet windows_;
 
   // The work area in the coordinates of |window_|.
   gfx::Rect work_area_in_parent_;
 
   // True if this workspace is currently in fullscreen mode.
   bool is_fullscreen_;
 
+  // A window which covers the full container and which gets inserted behind the
+  // topmost visible window.
+  scoped_ptr<WorkspaceLayoutManagerDelegate> backdrop_delegate_;
+
   DISALLOW_COPY_AND_ASSIGN(WorkspaceLayoutManager);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_WORKSPACE_WORKSPACE_LAYOUT_MANAGER_H_