Fix crash in ReparentItemToAnotherFolder() on Windows app list.

ui/app_list/views/apps_grid_view.cc

Index: ui/app_list/views/apps_grid_view.cc
diff --git a/ui/app_list/views/apps_grid_view.cc b/ui/app_list/views/apps_grid_view.cc
index 5a620a6270152c26c6b3aaf8ed0ec9a953d12074..ad7858345fc8062008cb28189e6a763495fe4dda 100644
--- a/ui/app_list/views/apps_grid_view.cc
+++ b/ui/app_list/views/apps_grid_view.cc
@@ -1680,14 +1680,17 @@ void AppsGridView::ReparentItemToAnotherFolder(views::View* item_view,
   AppListFolderItem* source_folder =
       static_cast<AppListFolderItem*>(item_list_->FindItem(source_folder_id));
 
+  AppListItemView* target_view =
+      static_cast<AppListItemView*>(GetViewAtSlotOnCurrentPage(target.slot));
+  if (!target_view)
+    return;

[tapted, 2014/05/09 02:55:47]

I think this will ~leak the observer removed up on line 1675 - should be OK just
to move this up to the top of the function though.

[calamity, 2014/05/09 03:13:02]

Done.

+
   // Remove the source folder view if there is only 1 item in it, since the
   // source folder will be deleted after its only child item merged into the
   // target item.
   if (source_folder->ChildItemCount() == 1u)
     DeleteItemViewAtIndex(view_model_.GetIndexOfView(activated_item_view()));
 
-  AppListItemView* target_view =
-      static_cast<AppListItemView*>(GetViewAtSlotOnCurrentPage(target.slot));
   AppListItem* target_item = target_view->item();
 
   // Move item to the target folder.