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..0374d436fe0d88ba2345b1b6f99ff858ec15bf4d 100644
--- a/ui/app_list/views/app_list_main_view.cc
+++ b/ui/app_list/views/app_list_main_view.cc
@@ -266,6 +266,15 @@ void AppListMainView::UpdateCustomLauncherPageVisibility() {
   }
 }
 
+// Removes AppItemList from folder's AppsGridView before the folder is deleted.
+void AppListMainView::OnSingleItemFolderWillBeDeleted() {
+  AppsGridView* folder_grid_view = contents_view_->apps_container_view()
+                                       ->app_list_folder_view()
+                                       ->items_grid_view();
+  if (folder_grid_view)
+    folder_grid_view->SetItemList(nullptr);  // removes observer
+}

[Greg Levin, 2015/03/25 21:58:16]

This seems like a slightly awkward way to get this done, but we hit a debug
break (in the destructor of an observer) if we don't remove the folder's
AppItemList from its AppsGridView before it's removed, and I didn't see a better
way to call into the views from the model.

[stevenjb, 2015/03/25 22:24:01]

This is indeed very awkward. It's also unclear to me exactly what this is doing.
It seems to be making an assumption that the active view is going to be deleted,
but that isn't necessarily the case is it? A sync event could uninstall an app
in a different folder, in which case the SetItemList seems like it would be bad.

Instead, I think that the model needs to signal when a specific folder is going
to be deleted so that the view can simply close it if it is open/visible. Does
that make sense?

[Greg Levin, 2015/03/26 19:45:11]

Done?  I'm still calling SetItemList(nullptr), because simply closing the open
folder does not remove the AppsGridView as an observer of the folder's
AppListItemList (which is about to be deleted).  However, I am verifying that
the folder to be deleted is actually the currently displayed folder.

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