Cleanup mojo Wallpaper interfaces for mash.

chrome/browser/chromeos/background/ash_wallpaper_delegate.cc

Index: chrome/browser/chromeos/background/ash_wallpaper_delegate.cc
diff --git a/chrome/browser/chromeos/background/ash_wallpaper_delegate.cc b/chrome/browser/chromeos/background/ash_wallpaper_delegate.cc
index 98ce8641310c370db16864734336d822c7210e10..780106103219728fdbb5bb29a046a03f525fb245 100644
--- a/chrome/browser/chromeos/background/ash_wallpaper_delegate.cc
+++ b/chrome/browser/chromeos/background/ash_wallpaper_delegate.cc
@@ -86,11 +86,6 @@ class WallpaperDelegate : public ash::WallpaperDelegate {
     chromeos::WallpaperManager::Get()->InitializeWallpaper();
   }
 
-  void OpenSetWallpaperPage() override {
-    if (CanOpenSetWallpaperPage())
-      wallpaper_manager_util::OpenWallpaperManager();
-  }
-
   bool CanOpenSetWallpaperPage() override {
     const LoginState* login_state = LoginState::Get();
     const LoginState::LoggedInUserType user_type =