1 files changed, 42 insertions, 0 deletions
diff --git a/dom/animation/test/mozilla/test_mainthread_synchronization_pref.html b/dom/animation/test/mozilla/test_mainthread_synchronization_pref.html
new file mode 100644
index 0000000000..3653fd9536
--- /dev/null
+++ b/dom/animation/test/mozilla/test_mainthread_synchronization_pref.html
@@ -0,0 +1,42 @@
+<!doctype html>
+<meta charset=utf-8>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../testcommon.js"></script>
+<style>
+.compositable {
+  /* Element needs geometry to be eligible for layerization */
+  width: 100px;
+  height: 100px;
+  background-color: white;
+}
+</style>
+<body>
+<div id="log"></div>
+<script>
+'use strict';
+
+promise_test(async t => {
+  await SpecialPowers.pushPrefEnv({
+    set: [[ 'dom.animations.mainthread-synchronization-with-geometric-animations', false ]]
+  });
+
+  const elemA = addDiv(t, { class: 'compositable' });
+  const elemB = addDiv(t, { class: 'compositable' });
+
+  const animA = elemA.animate({ transform: [ 'translate(0px)',
+                                             'translate(100px)' ] },
+                              100 * MS_PER_SEC);
+  const animB = elemB.animate({ marginLeft: [ '0px', '100px' ] },
+                              100 * MS_PER_SEC);
+
+  await waitForPaints();
+
+  assert_true(SpecialPowers.wrap(animA).isRunningOnCompositor,
+      'Transform animation should not synchronize with margin-left animation ' +
+      'created within the same tick with disabling the corresponding pref');
+}, 'Transform animation should not synchronize with margin-left animation '
+   + 'created within the same tick with disabling the corresponding pref');
+
+</script>
+</body>