Nonnative FileDialog doesn't restore sidebar URLs

QFileDialog saves its state via QSettings, including the folders in the sidebar. Unfortunately it no longer restores the sidebar folders. This used to work in 5.1.

QFileDialogPrivate::init() reads the settings and restores state via QFileDialog::restoreState(). restoreState() restores the selected folder but does not restore the sidebar if the dialog is in native mode. However, at the point when init() is called (from the constructors) the dialog will always be in native mode.

Possible fix: restoreState() could store the sidebar URLs in QFileDialogOptions and createWidgets() could restore them when the nonnative dialog is activated.