Revert of mash: Remove ChromeLauncherController's |id_to_item_controller_map_|.

ash/common/shelf/shelf_model.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/common/shelf/shelf_model.h"
 
 #include <algorithm>
 
 #include "ash/common/shelf/shelf_model_observer.h"
 #include "ash/public/cpp/shelf_item_delegate.h"
@@ skipping 52 matching lines @@
   items_[index].id = next_id_++;
   for (auto& observer : observers_)
     observer.ShelfItemAdded(index);
   return index;
 }
 
 void ShelfModel::RemoveItemAt(int index) {
   DCHECK(index >= 0 && index < item_count());
   ShelfItem old_item(items_[index]);
   items_.erase(items_.begin() + index);
-  id_to_item_delegate_map_.erase(old_item.id);
+  RemoveShelfItemDelegate(old_item.id);
+  // TODO(jamescook): Fold this into ShelfItemRemoved in existing observers.
+  for (auto& observer : observers_)
+    observer.OnSetShelfItemDelegate(old_item.id, nullptr);
   for (auto& observer : observers_)
     observer.ShelfItemRemoved(index, old_item);
 }
 
 void ShelfModel::Move(int index, int target_index) {
   if (index == target_index)
     return;
   // TODO: this needs to enforce valid ranges.
   ShelfItem item(items_[index]);
   items_.erase(items_.begin() + index);
@@ skipping 66 matching lines @@
   ShelfItem weight_dummy;
   weight_dummy.type = TYPE_APP_PANEL;
   return std::lower_bound(items_.begin(), items_.end(), weight_dummy,
                           CompareByWeight) -
          items_.begin();
 }
 
 void ShelfModel::SetShelfItemDelegate(
     ShelfID id,
     std::unique_ptr<ShelfItemDelegate> item_delegate) {
-  if (item_delegate)
-    item_delegate->set_shelf_id(id);
-  // This assignment replaces any ShelfItemDelegate already registered for |id|.
+  // If another ShelfItemDelegate is already registered for |id|, we assume
+  // that this request is replacing ShelfItemDelegate for |id| with
+  // |item_delegate|.
+  RemoveShelfItemDelegate(id);
+
+  for (auto& observer : observers_)
+    observer.OnSetShelfItemDelegate(id, item_delegate.get());
+
   id_to_item_delegate_map_[id] = std::move(item_delegate);
 }
 
 ShelfItemDelegate* ShelfModel::GetShelfItemDelegate(ShelfID id) {
   if (id_to_item_delegate_map_.find(id) != id_to_item_delegate_map_.end())
     return id_to_item_delegate_map_[id].get();
   return nullptr;
 }
 
 void ShelfModel::AddObserver(ShelfModelObserver* observer) {
@@ skipping 15 matching lines @@
                        items_.begin(),
                    static_cast<ShelfItems::difference_type>(index));
   index = std::min(std::upper_bound(items_.begin(), items_.end(), weight_dummy,
                                     CompareByWeight) -
                        items_.begin(),
                    static_cast<ShelfItems::difference_type>(index));
 
   return index;
 }
 
+void ShelfModel::RemoveShelfItemDelegate(ShelfID id) {
+  if (id_to_item_delegate_map_.find(id) != id_to_item_delegate_map_.end())
+    id_to_item_delegate_map_.erase(id);
+}
+
 }  // namespace ash