Bug 1226193 - Fix test_animation_observers.html timing out on Fennec with C++APZ enabled. r=heycam

Fix: INFO TEST-UNEXPECTED-FAIL | dom/animation/test/chrome/test_animation_observers.html | Test timed out.
By extending animation observer timeout.

--HG--
extra : commitid : GEfsdBOqqsu

dom/animation/test/chrome/test_animation_observers.html

@@ -1450,7 +1450,7 @@ addAsyncAnimTest("tree_ordering", { observe: div, subtree: true }, function*() {
 });
 
 // Run the tests.
-
+SimpleTest.requestLongerTimeout(2);
 SimpleTest.waitForExplicitFinish();
 
 runAllAsyncTests().then(function() {