Implement user selected wallpaper feature.

ash/desktop_background/desktop_background_controller.h

Index: ash/desktop_background/desktop_background_controller.h
diff --git a/ash/desktop_background/desktop_background_controller.h b/ash/desktop_background/desktop_background_controller.h
index b31a21464120ef1ecdff7e6f8e64f0ecb3c23329..4cc2e9cfb7862fb132d1a898d8c9f40685060444 100644
--- a/ash/desktop_background/desktop_background_controller.h
+++ b/ash/desktop_background/desktop_background_controller.h
@@ -51,6 +51,9 @@ class ASH_EXPORT DesktopBackgroundController {
   // wallpaper after loaded.
   void SetDefaultWallpaper(int index);
 
+  // Called when user selects a file from file system or changes the layout.

[flackr, 2012/05/09 21:26:16]

Describe what the function does, after which you can mention when it's called.
FYI some of the other comments in this file are wrong, should be "Cancels
the..", "Loads logged in..".

[bshe, 2012/05/10 16:10:26]

Done.

+  void SetCustomWallpaper(const SkBitmap& wallpaper, WallpaperLayout layout);
+
   // Cancel the current wallpaper loading operation.
   void CancelPendingWallpaperOperation();