Add additional CHECKs to AppListModel.

ui/app_list/app_list_item_list.cc

 // Copyright (c) 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 "ui/app_list/app_list_item_list.h"
 
 #include "ui/app_list/app_list_item.h"
 
 namespace app_list {
 
@@ skipping 148 matching lines @@
                     observers_,
                     OnListItemAdded(index, item));
   return item;
 }
 
 void AppListItemList::DeleteItem(const std::string& id) {
   scoped_ptr<AppListItem> item = RemoveItem(id);
   // |item| will be deleted on destruction.
 }
 
-scoped_ptr<AppListItem> AppListItemList::RemoveItem(
-    const std::string& id) {
+scoped_ptr<AppListItem> AppListItemList::RemoveItem(const std::string& id) {
   size_t index;
-  if (FindItemIndex(id, &index))
-    return RemoveItemAt(index);
-
-  return scoped_ptr<AppListItem>();
+  if (!FindItemIndex(id, &index))
+    LOG(FATAL) << "RemoveItem: Not found: " << id;
+  return RemoveItemAt(index);
 }
 
 scoped_ptr<AppListItem> AppListItemList::RemoveItemAt(size_t index) {
-  DCHECK_LT(index, item_count());
+  CHECK_LT(index, item_count());
   AppListItem* item = app_list_items_[index];
   app_list_items_.weak_erase(app_list_items_.begin() + index);
   FOR_EACH_OBSERVER(AppListItemListObserver,
                     observers_,
                     OnListItemRemoved(index, item));
   return make_scoped_ptr<AppListItem>(item);
 }
 
 void AppListItemList::DeleteItemAt(size_t index) {
   scoped_ptr<AppListItem> item = RemoveItemAt(index);
@@ skipping 48 matching lines @@
     else
       cur->set_position(prev->position().CreateAfter());
     prev = cur;
   }
   FOR_EACH_OBSERVER(AppListItemListObserver,
                     observers_,
                     OnListItemMoved(index, index, app_list_items_[index]));
 }
 
 }  // namespace app_list