In order for the Filechooser Location widget to work two
things need to be setup, which only the FileChooserDialog
does:
* subscribe to Widget's "response-requested" signal
* call should_respond () hook from top-level window's
default handler.
The Location Entry emits "activates-default". In case of
the Dialog, that calls the dialogs response callback,
which then calls ` _gtk_file_chooser_embed_should_respond`.
That handles changes made by the user to the location entry.
-=-
Gtk::FileChooserWidget does not handle this, "response-requested"
signal is not exposed, nor is _gtk_file_chooser_embed_should_respond
available outside Gtk.
This change at least selects the file in the treeview, which
allows further handling, without interfering with FileChooserDialog's
behavior.
