WP_Customize_Nav_Menus::print_templates

		$params         = wp_unslash( $_POST['params'] );
		$illegal_params = array_diff( array_keys( $params ), array( 'post_type', 'post_title' ) );
		if ( ! empty( $illegal_params ) ) {
			wp_send_json_error( 'illegal_params', 400 );
		}

		$params = array_merge(
			array(
				'post_type'  => '',
				'post_title' => '',
			),
			$params
		);

		if ( empty( $params['post_type'] ) || ! post_type_exists( $params['post_type'] ) ) {
			status_header( 400 );
			wp_send_json_error( 'missing_post_type_param' );
		}

		$post_type_object = get_post_type_object( $params['post_type'] );
		if ( ! current_user_can( $post_type_object->cap->create_posts ) || ! current_user_can( $post_type_object->cap->publish_posts ) ) {
			status_header( 403 );
			wp_send_json_error( 'insufficient_post_permissions' );
		}

		$params['post_title'] = trim( $params['post_title'] );
		if ( '' === $params['post_title'] ) {
			status_header( 400 );
			wp_send_json_error( 'missing_post_title' );
		}

		$r = $this->insert_auto_draft_post( $params );
		if ( is_wp_error( $r ) ) {
			$error = $r;
			if ( ! empty( $post_type_object->labels->singular_name ) ) {
				$singular_name = $post_type_object->labels->singular_name;
			} else {
				$singular_name = __( 'Post' );
			}

			$data = array(
				/* translators: 1: Post type name, 2: Error message. */
				'message' => sprintf( __( '%1$s could not be created: %2$s' ), $singular_name, $error->get_error_message() ),
			);
			wp_send_json_error( $data );
		} else {
			$post = $r;
			$data = array(
				'post_id' => $post->ID,
				'url'     => get_permalink( $post->ID ),
			);
			wp_send_json_success( $data );
		}
	}

	/**
	 * Print the JavaScript templates used to render Menu Customizer components.
	 *
	 * Templates are imported into the JS use wp.template.
	 *
	 * @since 4.3.0
	 */
	public function print_templates() {
		?>
		<script type="text/html" id="tmpl-available-menu-item">
			<li id="menu-item-tpl-{{ data.id }}" class="menu-item-tpl" data-menu-item-id="{{ data.id }}">
				<div class="menu-item-bar">
					<div class="menu-item-handle">
						<span class="item-type" aria-hidden="true">{{ data.type_label }}</span>