Bug 1341985 - Use registerCleanupFunction to restore to normal refresh mode. r=heycam

Otherwise, the refresh driver left under test mode when a javascript error
occurs in the middle of tests.

MozReview-Commit-ID: J7oUuuYhTZ1

--HG--
extra : rebase_source : 16467b780007eeacd0e70f581ca01ab6f778dfd7

layout/style/test/test_animations.html

@@ -231,6 +231,10 @@ window.new_div = function(style) {
 // take over the refresh driver right from the start.
 advance_clock(0);
 
+SimpleTest.registerCleanupFunction(() => {
+  SpecialPowers.DOMWindowUtils.restoreNormalRefresh();
+});
+
 /*
  * css3-animations:  2. Animations
  * http://dev.w3.org/csswg/css3-animations/#animations
@@ -2095,8 +2099,6 @@ div.style.animation = "\"none\" 1s linear";
 is(cs.getPropertyValue("left"), "7px", "animation name 'none' as string is accepted");
 done_div();
 
-SpecialPowers.DOMWindowUtils.restoreNormalRefresh();
-
 </script>
 </pre>
 </body>