mash: Use mojo for ShelfItemDelegate and [app] MenuItem.

ash/common/shelf/shelf_model_observer.h

Index: ash/common/shelf/shelf_model_observer.h
diff --git a/ash/common/shelf/shelf_model_observer.h b/ash/common/shelf/shelf_model_observer.h
index 794300da4900b36a740797c60d518d1021c3680a..fa3e2bf853fdd0adb4be88c39590eec9a003fa5b 100644
--- a/ash/common/shelf/shelf_model_observer.h
+++ b/ash/common/shelf/shelf_model_observer.h
@@ -11,7 +11,10 @@
 namespace ash {
 
 struct ShelfItem;
+
+namespace mojom {
 class ShelfItemDelegate;
+}
 
 class ASH_EXPORT ShelfModelObserver {
  public:
@@ -34,8 +37,9 @@ class ASH_EXPORT ShelfModelObserver {
   // |item_delegate| can be null.
   // NOTE: This is added a temporary fix for M39 to fix crbug.com/429870.
   // TODO(skuhne): Find the real reason for this problem and remove this fix.
-  virtual void OnSetShelfItemDelegate(ShelfID id,
-                                      ShelfItemDelegate* item_delegate) = 0;
+  virtual void OnSetShelfItemDelegate(
+      ShelfID id,
+      mojom::ShelfItemDelegate* item_delegate) = 0;
 
  protected:
   virtual ~ShelfModelObserver() {}