Language_Pack_Upgrader::async_upgrade( false|WP_Upgrader $upgrader = false )

	public static function async_upgrade( $upgrader = false ) {
		// Avoid recursion.
		if ( $upgrader && $upgrader instanceof Language_Pack_Upgrader ) {
			return;
		}

		// Nothing to do?
		$language_updates = wp_get_translation_updates();
		if ( ! $language_updates ) {
			return;
		}

		/*
		 * Avoid messing with VCS installations, at least for now.
		 * Noted: this is not the ideal way to accomplish this.
		 */
		$check_vcs = new WP_Automatic_Updater;
		if ( $check_vcs->is_vcs_checkout( WP_CONTENT_DIR ) ) {
			return;
		}

		foreach ( $language_updates as $key => $language_update ) {
			$update = ! empty( $language_update->autoupdate );

			/**
			 * Filters whether to asynchronously update translation for core, a plugin, or a theme.
			 *
			 * @since WP-4.0.0
			 *
			 * @param bool   $update          Whether to update.
			 * @param object $language_update The update offer.
			 */
			$update = apply_filters( 'async_update_translation', $update, $language_update );

			if ( ! $update ) {
				unset( $language_updates[ $key ] );
			}
		}

		if ( empty( $language_updates ) ) {
			return;
		}

		// Re-use the automatic upgrader skin if the parent upgrader is using it.
		if ( $upgrader && $upgrader->skin instanceof Automatic_Upgrader_Skin ) {
			$skin = $upgrader->skin;
		} else {
			$skin = new Language_Pack_Upgrader_Skin( array(
				'skip_header_footer' => true,
			) );
		}

		$lp_upgrader = new Language_Pack_Upgrader( $skin );
		$lp_upgrader->bulk_upgrade( $language_updates );
	}