Enable user change background image in settings page in Aura build.

chrome/browser/chromeos/login/user_manager.h

Index: chrome/browser/chromeos/login/user_manager.h
diff --git a/chrome/browser/chromeos/login/user_manager.h b/chrome/browser/chromeos/login/user_manager.h
index 6e70d7cccc4a2a00169a9fe6400573e316668955..233921b8cc119f4d8c432691fce19becf84e7b0d 100644
--- a/chrome/browser/chromeos/login/user_manager.h
+++ b/chrome/browser/chromeos/login/user_manager.h
@@ -99,6 +99,17 @@ class UserManager : public ProfileDownloaderDelegate,
   // Otherwise, returns |username| itself.
   std::string GetUserDisplayEmail(const std::string& username) const;
 
+  // Returns the index of the default wallpapers saved in local state for user
+  // |username| if it is known (was previousely set by
+  // |SaveWallpaperToLocalState| call).
+  // Otherwise, returns default wallpaper index.
+  int GetUserWallpaper(const std::string& username);
+
+  // Sets user wallpaper to the default wallpaper with index |wallpaper_index|,
+  // sends DESKTOP_BACKGROUND_CHANGED notification and updates Local State.
+  void SaveWallpaperDefaultIndex(const std::string& username,
+                                 int wallpaper_index);
+
   // Sets user image to the default image with index |image_index|, sends
   // LOGIN_USER_IMAGE_CHANGED notification and updates Local State.
   void SaveUserDefaultImageIndex(const std::string& username, int image_index);