reland: mash: Remove ChromeLauncherController's |id_to_item_controller_map_|.

ash/shelf/shelf_model_observer.h

Index: ash/shelf/shelf_model_observer.h
diff --git a/ash/shelf/shelf_model_observer.h b/ash/shelf/shelf_model_observer.h
index 410254c041872f22b5c2303818fbabd23aad55a2..fafb45c707e77b1c19f2e8e50837039ebb1c5de1 100644
--- a/ash/shelf/shelf_model_observer.h
+++ b/ash/shelf/shelf_model_observer.h
@@ -11,7 +11,6 @@
 namespace ash {
 
 struct ShelfItem;
-class ShelfItemDelegate;
 
 class ASH_EXPORT ShelfModelObserver {
  public:
@@ -26,17 +25,9 @@ class ASH_EXPORT ShelfModelObserver {
   // of the arguments.
   virtual void ShelfItemMoved(int start_index, int target_index) = 0;
 
-  // Invoked when the state of an item changes. |old_item| is the item
-  // before the change.
+  // Invoked after an item changes. |old_item| is the item before the change.
   virtual void ShelfItemChanged(int index, const ShelfItem& old_item) = 0;
 
-  // Gets called when a ShelfItemDelegate gets changed. Note that
-  // |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;
-
  protected:
   virtual ~ShelfModelObserver() {}
 };