Fix failing DrmEngine unit test on Edge
Fix failing DrmEngine unit test on Edge

Caused by the fix from issue #634

Change-Id: I5a622af126245ca7849cc3894edb2d465cc21a37

indiereign/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,TheModMaker/shaka-player,tvoli/shaka-player,indiereign/shaka-player,tvoli/shaka-player,brightcove/shaka-player,shaka-project/shaka-player,vimond/shaka-player,TheModMaker/shaka-player,TobbeEdgeware/shaka-player,shaka-project/shaka-player,TheModMaker/shaka-player,tvoli/shaka-player,russitto/shaka-player,TobbeEdgeware/shaka-player,TheModMaker/shaka-player,shaka-project/shaka-player,brightcove/shaka-player,Ross-cz/shaka-player,vimond/shaka-player,brightcove/shaka-player,Ross-cz/shaka-player,Ross-cz/shaka-player,TobbeEdgeware/shaka-player,vimond/shaka-player,indiereign/shaka-player,russitto/shaka-player,russitto/shaka-player