Cleanup mojo Wallpaper interfaces for mash.

ash/mus/context_menu_mus.cc

Index: ash/mus/context_menu_mus.cc
diff --git a/ash/mus/context_menu_mus.cc b/ash/mus/context_menu_mus.cc
index b3284194dbbc59c81ae7b31506aef8c994067632..32e12dc63cfa992b60f75d2fe1c6f0c7e016f332 100644
--- a/ash/mus/context_menu_mus.cc
+++ b/ash/mus/context_menu_mus.cc
@@ -5,6 +5,7 @@
 #include "ash/mus/context_menu_mus.h"
 
 #include "ash/common/shelf/wm_shelf.h"
+#include "ash/common/wallpaper/wallpaper_controller.h"
 #include "ash/common/wallpaper/wallpaper_delegate.h"
 #include "ash/common/wm_shell.h"
 #include "ash/public/cpp/shelf_types.h"
@@ -47,7 +48,7 @@ void ContextMenuMus::ExecuteCommand(int command_id, int event_flags) {
                                        ? SHELF_AUTO_HIDE_BEHAVIOR_NEVER
                                        : SHELF_AUTO_HIDE_BEHAVIOR_ALWAYS);
   } else if (command_id == MENU_CHANGE_WALLPAPER) {
-    WmShell::Get()->wallpaper_delegate()->OpenSetWallpaperPage();
+    WmShell::Get()->wallpaper_controller()->OpenSetWallpaperPage();
   }
 }