mash: Fold ShelfItemDelegateManager into ShelfModel

ash/shelf/shelf_view.h

Index: ash/shelf/shelf_view.h
diff --git a/ash/shelf/shelf_view.h b/ash/shelf/shelf_view.h
index c57dc156ae5c5771501fe08676aaaf7bfeba17bd..ce66fef3245357d86abd7d2fe63a7582eda2ab67 100644
--- a/ash/shelf/shelf_view.h
+++ b/ash/shelf/shelf_view.h
@@ -288,6 +288,8 @@ class ASH_EXPORT ShelfView : public views::View,
   void ShelfItemRemoved(int model_index, ShelfID id) override;
   void ShelfItemChanged(int model_index, const ShelfItem& old_item) override;
   void ShelfItemMoved(int start_index, int target_index) override;
+  void OnSetShelfItemDelegate(ShelfID id,
+                              ShelfItemDelegate* item_delegate) override;
 
   // Overridden from InkDropButtonListener:
   void ButtonPressed(views::Button* sender,
@@ -445,9 +447,6 @@ class ASH_EXPORT ShelfView : public views::View,
   // The rip off view when a snap back operation is underway.
   views::View* snap_back_from_rip_off_view_;
 
-  // Holds ShelfItemDelegateManager.
-  ShelfItemDelegateManager* item_manager_;
-
   // True when this ShelfView is used for Overflow Bubble.
   bool overflow_mode_;