Show the title and the items in the user's language (TYP-1287). Only for a menu of the editor's own choices — alignments, fit modes, blend modes. Never for one that lists a document's fonts, styles or swatches: those are names, not words to translate.
The same normalisation as Popupmenu.setTitle, and needed for its own reason: this override hands the value to an input field, which does not throw — it renders the literal text "undefined" into the box instead. Silent and wrong beats loud and wrong only when the value is real.
owner_dialogis passed straight to Popupmenu, which hands it to its MenuControler: a menu built for a dialog dispatches to that dialog's menu_item_selected() instead of the editor's global one. Popupmenu has always taken it; this subclass simply did not pass it on, so an editable popup inside a dialog was routed to the editor's handlers — which act on the current selection, not on the dialog.