Revert of Wallpaper manager now observing user child user status to update default wallpaper.

chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h

Index: chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h
diff --git a/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h b/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h
index c510b91ef6dc4598357e6d3de9e90ce679903b34..ace1f829e6878258cfb82beb647d994d04296740 100644
--- a/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h
+++ b/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.h
@@ -21,7 +21,6 @@
 #include "chrome/browser/chromeos/settings/cros_settings.h"
 #include "components/user_manager/user.h"
 #include "components/user_manager/user_image/user_image.h"
-#include "components/user_manager/user_manager.h"
 #include "components/wallpaper/wallpaper_layout.h"
 #include "components/wallpaper/wallpaper_manager_base.h"
 #include "content/public/browser/notification_observer.h"
@@ -31,9 +30,7 @@
 
 namespace chromeos {
 
-class WallpaperManager :
-    public wallpaper::WallpaperManagerBase,
-    public user_manager::UserManager::UserSessionStateObserver {
+class WallpaperManager : public wallpaper::WallpaperManagerBase {
  public:
   class PendingWallpaper;
 
@@ -118,9 +115,6 @@
   // Returns queue size.
   size_t GetPendingListSizeForTesting() const override;
 
-  // Overridden from user_manager::UserManager::UserSessionStateObserver:
-  void UserChangedChildStatus(user_manager::User* user) override;
-
  private:
   friend class TestApi;
   friend class WallpaperManagerBrowserTest;