Bug 1470350. Enable delaytest.html tests again. r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D70105

--HG--
extra : moz-landing-system : lando

image/test/reftest/apng/reftest.list

@@ -2,5 +2,5 @@
 #
 # delaytest.html delays the reftest snapshot to allow time for the
 # animation to complete.
-random == delaytest.html?bug411852-1.png bug411852-1-ref.html
-random == delaytest.html?bug546272.png bug546272-ref.html
+== delaytest.html?bug411852-1.png bug411852-1-ref.html
+== delaytest.html?bug546272.png bug546272-ref.html

image/test/reftest/gif/reftest.list

@@ -14,7 +14,7 @@
 
 # a transparent gif that disposes previous frames with clear; we must properly
 # clear each frame to pass.
-random == delaytest.html?transparent-animation.gif transparent-animation-finalframe.html # incorrect timing dependence (bug 558678)
+== delaytest.html?transparent-animation.gif transparent-animation-finalframe.html
 
 # test for bug 641198
 skip == test_bug641198.html animation2a-finalframe.gif  # Disabled; see bug 1120144.