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

ash/desktop_background/desktop_background_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_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_CONTROLLER_H_
 #define ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_CONTROLLER_H_
 
 #include "ash/ash_export.h"
 #include "ash/desktop_background/desktop_background_resources.h"
 #include "ash/wm/window_animations.h"
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkColor.h"
+#include "ui/compositor/layer.h"
 #include "ui/gfx/image/image_skia.h"
 
 namespace aura {
 class RootWindow;
 }
 
 namespace ash {
 
 class UserWallpaperDelegate {
  public:
@@ skipping 61 matching lines @@
   void SetDesktopBackgroundSolidColorMode(SkColor color);
 
   // Creates an empty wallpaper. Some tests require a wallpaper widget is ready
   // when running. However, the wallpaper widgets are now created asynchronously
   // . If loading a real wallpaper, there are cases that these tests crash
   // because the required widget is not ready. This function synchronously
   // creates an empty widget for those tests to prevent crashes. An example test
   // is SystemGestureEventFilterTest.ThreeFingerSwipe.
   void CreateEmptyWallpaper();
 
+  // Move all desktop widgets to locked container.
+  void MoveDesktopToLockedContainer();
+
+  // Move all desktop widgets to unlocked container.
+  void MoveDesktopToUnlockedContainer();
+
  private:
   // An operation to asynchronously loads wallpaper.
   class WallpaperOperation;
 
   struct WallpaperData;
 
-  // Creates a new background widget using the current wallpapaer image and
-  // use it as a background of the |root_window|. Deletes the old widget if any.
-  void SetDesktopBackgroundImage(aura::RootWindow* root_window);
-
-  // Update the background of all root windows using the current wallpaper image
-  // in |current_wallpaper_|.
-  void UpdateDesktopBackgroundImageMode();
+  // Creates view for all root windows, or notifies them to repaint if they
+  // already exist.
+  void SetDesktopBackgroundImageMode();
 
   // Creates a new background widget and sets the background mode to image mode.
   // Called after wallpaper loaded successfully.
   void OnWallpaperLoadCompleted(scoped_refptr<WallpaperOperation> wo);
 
+  // Add layer with solid |color| to container |container_id| in |root_window|

[bshe, 2012/07/30 21:38:20]

nit: Add/Adds

+  ui::Layer* SetColorLayerForContainer(SkColor color,
+                                 aura::RootWindow* root_window,
+                                 int container_id);

[bshe, 2012/07/30 21:38:20]

nit: indent is off here.

+
+  // Creates and adds component for current mode (either Widget or Layer) to
+  // |root_window|.
+  void InstallComponent(aura::RootWindow* root_window);
+
+  // Creates and adds component for current mode (either Widget or Layer) to
+  // all root windows.
+  void InstallComponentForAllWindows();
+
+  // Moves all descktop components from one container to other across all root
+  // windows.
+  void ReparentBackgroundWidgets(int src_container, int dst_container);
+
+  // Returns id for background container for unlocked and locked states.
+  int GetBackgroundContainerId(bool locked);
+
   // Can change at runtime.
+  bool locked_;
+
   BackgroundMode desktop_background_mode_;
 
   SkColor background_color_;
 
   // The current wallpaper.
   scoped_ptr<WallpaperData> current_wallpaper_;
 
   scoped_refptr<WallpaperOperation> wallpaper_op_;
 
   base::WeakPtrFactory<DesktopBackgroundController> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopBackgroundController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_CONTROLLER_H_