diff -r 000000000000 -r 6474c204b198 layout/reftests/position-dynamic-changes/relative/animate.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/reftests/position-dynamic-changes/relative/animate.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,32 @@
+var rfa = null;
+if (window.requestAnimationFrame) {
+  rfa = requestAnimationFrame;
+} else if (window.mozRequestAnimationFrame) {
+  rfa = mozRequestAnimationFrame;
+} else if (window.webkitRequestAnimationFrame) {
+  rfa = webkitRequestAnimationFrame;
+} else if (window.msRequestAnimationFrame) {
+  rfa = msRequestAnimationFrame;
+} else if (window.oRequestAnimationFrame) {
+  rfa = oRequestAnimationFrame;
+}
+
+function animate(params, count) {
+  rfa(function() {
+    animateStep(params, count);
+  });
+}
+
+function animateStep(params, count) {
+  if (!count) {
+    document.documentElement.removeAttribute("class");
+    return;
+  }
+  var rel = document.getElementById("rel");
+  for (prop in params) {
+    rel.style[prop] = (parseInt(rel.style[prop]) + params[prop]) + "px";
+  }
+  rfa(function() {
+    animateStep(params, count - 10);
+  });
+}