NSSavePanel (and NSOpenPanel, as a subclass) supports a `message` (via `setMessage:message` in Obj-C), which allows a message to be displayed even when the panel is attached to a parent. Right now, `title` is useless for attached dialogs.

atom/browser/api/atom_api_dialog.cc
#include <string>
#include <utility>
#include <vector>
#include "atom/browser/api/atom_api_window.h"
#include "atom/browser/native_window.h"
#include "atom/browser/ui/file_dialog.h"
#include "atom/browser/ui/message_box.h"
#include "atom/common/native_mate_converters/callback.h"
#include "atom/common/native_mate_converters/file_path_converter.h"
#include "atom/common/native_mate_converters/image_converter.h"
#include "native_mate/dictionary.h"
#include "atom/common/node_includes.h"
namespace mate {
template<>
struct Converter<file_dialog::Filter> {
  static bool FromV8(v8::Isolate* isolate,