Git commits in Moodle 3.5.4 by Mark Nelson

commit 551975b2acd0e42508593699ef294c837285a4b3
Author: Mark Nelson <markn@moodle.com>
Date:   Tue, 11 Dec 2018 14:22:40 +0800
Tag:    v3.5.4

MDL-64357 ltiservice_gradebookservices: updated unit tests


commit d5901aa09cb9bb3b0fc6a06d0b34efe0098cc0e3
Author: Mark Nelson <markn@moodle.com>
Date:   Tue, 27 Nov 2018 17:17:41 +0800
Tag:    v3.5.4

MDL-64206 core: updated FB logo URL