Add a ListModel::Move.

ui/base/models/list_model.h

 // Copyright (c) 2012 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.
 
 #ifndef UI_BASE_MODELS_LIST_MODEL_H_
 #define UI_BASE_MODELS_LIST_MODEL_H_
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/memory/scoped_vector.h"
@@ skipping 44 matching lines @@
   void DeleteAt(size_t index) {
     delete RemoveAt(index);
   }
 
   // Removes and deletes all items from the model.
   void DeleteAll() {
     ScopedVector<ItemType> to_be_deleted(items_.Pass());
     NotifyItemsRemoved(0, to_be_deleted.size());
   }
 
+  // Moves the item at |index| to |target_index|. |target_index| is in terms
+  // of the model *after* the item at |index| is removed.
+  void Move(size_t index, size_t target_index) {
+    DCHECK_LT(index, item_count());
+    DCHECK_LT(target_index, item_count());
+
+    if (index == target_index)
+      return;
+
+    ItemType* item = items_[index];
+    items_.weak_erase(items_.begin() + index);
+    items_.insert(items_.begin() + target_index, item);
+    NotifyItemMoved(index, target_index);
+  }
+
   void AddObserver(ListModelObserver* observer) {
     observers_.AddObserver(observer);
   }
 
   void RemoveObserver(ListModelObserver* observer) {
     observers_.RemoveObserver(observer);
   }
 
   void NotifyItemsAdded(size_t start, size_t count) {
     FOR_EACH_OBSERVER(ListModelObserver,
                       observers_,
                       ListItemsAdded(start, count));
   }
 
   void NotifyItemsRemoved(size_t start, size_t count) {
     FOR_EACH_OBSERVER(ListModelObserver,
                       observers_,
                       ListItemsRemoved(start, count));
   }
 
+  void NotifyItemMoved(size_t index, size_t target_index) {
+    FOR_EACH_OBSERVER(ListModelObserver,
+                      observers_,
+                      ListItemMoved(index, target_index));
+  }
+
   void NotifyItemsChanged(size_t start, size_t count) {
     FOR_EACH_OBSERVER(ListModelObserver,
                       observers_,
                       ListItemsChanged(start, count));
   }
 
   size_t item_count() const { return items_.size(); }
 
   const ItemType* GetItemAt(size_t index) const {
     DCHECK_LT(index, item_count());
     return items_[index];
   }
   ItemType* GetItemAt(size_t index) {
     return const_cast<ItemType*>(
         const_cast<const ListModel<ItemType>*>(this)->GetItemAt(index));
   }
 
  private:
   ScopedVector<ItemType> items_;
   ObserverList<ListModelObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ListModel<ItemType>);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_MODELS_LIST_MODEL_H_