WP_Customize_Manager::add_state_query_params( string $url )

	public function add_state_query_params( $url ) {
		$parsed_original_url = wp_parse_url( $url );
		$is_allowed = false;
		foreach ( $this->get_allowed_urls() as $allowed_url ) {
			$parsed_allowed_url = wp_parse_url( $allowed_url );
			$is_allowed = (
				$parsed_allowed_url['scheme'] === $parsed_original_url['scheme']
				&&
				$parsed_allowed_url['host'] === $parsed_original_url['host']
				&&
				0 === strpos( $parsed_original_url['path'], $parsed_allowed_url['path'] )
			);
			if ( $is_allowed ) {
				break;
			}
		}

		if ( $is_allowed ) {
			$query_params = array(
				'customize_changeset_uuid' => $this->changeset_uuid(),
			);
			if ( ! $this->is_theme_active() ) {
				$query_params['customize_theme'] = $this->get_stylesheet();
			}
			if ( $this->messenger_channel ) {
				$query_params['customize_messenger_channel'] = $this->messenger_channel;
			}
			$url = add_query_arg( $query_params, $url );
		}

		return $url;
	}