Bug 1389439 - Part 2: Enable test_underlying-discrete-value.html on stylo. r=hiro

MozReview-Commit-ID: 8zqUHnoZvee

--HG--
extra : rebase_source : b0c372cc5badb5b2d0661a478c6bc2905cb481d2

dom/animation/test/mochitest.ini

@@ -117,7 +117,6 @@ skip-if = stylo
 [mozilla/test_transition_finish_on_compositor.html]
 skip-if = toolkit == 'android'
 [mozilla/test_underlying-discrete-value.html]
-skip-if = stylo
 [style/test_animation-seeking-with-current-time.html]
 [style/test_animation-seeking-with-start-time.html]
 [style/test_animation-setting-effect.html]