After uninstall, remove last item in Launcher folder

ui/app_list/views/app_list_main_view.cc

Index: ui/app_list/views/app_list_main_view.cc
diff --git a/ui/app_list/views/app_list_main_view.cc b/ui/app_list/views/app_list_main_view.cc
index dceae0faa72d4f49bddc4e827b990d5bc0c64783..ddc0b183ee4a8a36e80f0175abd6a6c926676b99 100644
--- a/ui/app_list/views/app_list_main_view.cc
+++ b/ui/app_list/views/app_list_main_view.cc
@@ -266,6 +266,26 @@ void AppListMainView::UpdateCustomLauncherPageVisibility() {
   }
 }
 
+// Issue 368111: Upon uninstall of 2nd-to-last folder item, reparent last child
+// to top and remove folder.
+void AppListMainView::OnAppListChildItemUninstalled(AppListFolderItem* parent) {
+  if (!parent || parent->ChildItemCount() != 1u)
+    return;
+
+  AppsGridView* top_grid_view =
+      contents_view_->apps_container_view()->apps_grid_view();
+  AppsGridView* folder_grid_view = contents_view_->apps_container_view()
+                                       ->app_list_folder_view()
+                                       ->items_grid_view();
+
+  model_->top_level_item_list()->RemoveObserver(top_grid_view);
+  folder_grid_view->SetItemList(nullptr);  // removes observer
+
+  top_grid_view->RemoveLastItemFromReparentItemFolderIfNecessary(parent->id());
+
+  model_->top_level_item_list()->AddObserver(top_grid_view);
+}
+

[Greg Levin, 2015/03/14 03:51:45]

When "drag app out of folder" uses
RemoveLastItemFromReparentItemFolderIfNecessary() to reparent the last remaining
item and remove the folder, it removes both AppsGridViews as AppListItemList
observers, and then adds the top level one back when it's done.  I'll admit, I
don't totally understand why all this is necessary, but it will crash if any of
these steps is left out.

[jennyz, 2015/03/17 21:16:48]

Yes, the views are the observers of its associated data model, when we make a
series changes to both data model and view, we don't want to data model changed
to cascading to all the views before the entire operation completes, and if the
associated data item is removed, it could cause crash as well. Typically, we
follow the sequence of: remove view observer from the data model, remove the
views if the model will be removed, make changes to data model, make the
necessary changes to the views, add the view observers back when all operations
are done.

[Greg Levin, 2015/03/23 22:04:50]

Ok, that makes sense.  Thanks!

 void AppListMainView::OnCustomLauncherPageEnabledStateChanged(bool enabled) {
   views::View* custom_page = contents_view_->custom_page_view();
   if (!custom_page)