Git commits in Moodle 3.9.0 by Frédéric Massart

commit ef1a9a21357f2b98bf92977a6ab1154d885cf914
Author: Frédéric Massart <fred@branchup.tech>
Date:   Tue, 03 Dec 2019 13:03:43 +0800
Tag:    v3.9.0-beta

MDL-67434 javascript: Use static get_string after recycling promise