2nd display should show the same background as login/lock screen:

ash/wm/root_window_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_ROOT_WINDOW_LAYOUT_MANAGER_H_
 #define ASH_WM_ROOT_WINDOW_LAYOUT_MANAGER_H_
 
+#include "ash/shell_window_ids.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/aura/layout_manager.h"
 
 namespace aura {
 class Window;
 }
 namespace gfx {
 class Rect;
 }
 namespace ui {
 class Layer;
 }
 namespace views {
 class Widget;
 }
 
 namespace ash {
 namespace internal {
 
 // A layout manager for the root window.
 // Resizes all of its immediate children to fill the bounds of the root window.
 class RootWindowLayoutManager : public aura::LayoutManager {
  public:
   explicit RootWindowLayoutManager(aura::Window* owner);
   virtual ~RootWindowLayoutManager();
 
-  views::Widget* background_widget() { return background_widget_; }
-  ui::Layer* background_layer() { return background_layer_.get(); }
-
-  // Sets the background to |widget|. Closes and destroys the old widget if it
-  // exists and differs from the new widget.
-  void SetBackgroundWidget(views::Widget* widget);
-
-  // Sets a background layer, taking ownership of |layer|.  This is provided as
-  // a lightweight alternative to SetBackgroundWidget(); layers can be simple
-  // colored quads instead of being textured.
-  void SetBackgroundLayer(ui::Layer* layer);
-
   // 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 visible) OVERRIDE;
   virtual void SetChildBounds(aura::Window* child,
                               const gfx::Rect& requested_bounds) OVERRIDE;
 
  private:
   aura::Window* owner_;
 
-  // May be NULL if we're not painting a background.
-  views::Widget* background_widget_;
-  scoped_ptr<ui::Layer> background_layer_;
-
   DISALLOW_COPY_AND_ASSIGN(RootWindowLayoutManager);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_WM_ROOT_WINDOW_LAYOUT_MANAGER_H_