Form submission handler for 'Delete' button in field_ui_field_edit_form().
function field_ui_field_edit_form_delete_submit($form, &$form_state) {
$destination = array();
if (isset($_GET['destination'])) {
$destination = drupal_get_destination();
unset($_GET['destination']);
}
$instance = $form['#instance'];
$form_state['redirect'] = array(
'admin/structure/types/manage/' . $instance['bundle'] . '/fields/' . $instance['field_name'] . '/delete',
array(
'query' => $destination,
),
);
}