Make an AddAll in ListModel.

ui/base/models/list_model.h

Index: ui/base/models/list_model.h
diff --git a/ui/base/models/list_model.h b/ui/base/models/list_model.h
index 9b4440d9a020d2db41d8bfb7adade37fe2ec173e..861d6ffd1e13d0a87d394aadd032d90777acdeec 100644
--- a/ui/base/models/list_model.h
+++ b/ui/base/models/list_model.h
@@ -34,6 +34,19 @@ class ListModel {
     AddAt(item_count(), item);
   }
 
+  // Add a vector of items to the end of the model. This triggers one
+  // notification after adding all items. No notification is sent if |new_items|
+  // is empty.
+  void AddAll(ScopedVector<ItemType> new_items) {
+    if (new_items.empty())
+      return;
+
+    const size_t count = item_count();
+    items_.insert(items_.end(), new_items.begin(), new_items.end());
+    new_items.weak_clear();
+    NotifyItemsAdded(count, items_.size() - count);
+  }
+
   // Removes an item at given |index| from the model. Note the removed item
   // is NOT deleted and it's up to the caller to delete it.
   ItemType* RemoveAt(size_t index) {