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diff --git a/layout/reftests/transform/partial-prerender-translate-3.html b/layout/reftests/transform/partial-prerender-translate-3.html
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+++ b/layout/reftests/transform/partial-prerender-translate-3.html
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+<!DOCTYPE html>
+<html class="reftest-wait reftest-no-flush">
+<meta name="viewport" content="width=device-width,minimum-scale=1,initial-scale=1">
+<!--
+  A test for a partial pre-rendered transform animation moves to a place where
+  the partial pre-rendered area is completely out of the viewport but still
+  there remains some amount of area of the entire transform element.
+  If we mis-recognize it as NOT a jank, checkerboading will happen.
+  -->
+<style>
+html {
+  overflow: hidden;
+}
+body {
+  margin: 0px;
+  padding: 0px;
+}
+@keyframes anim {
+  /* translate to a position the partial pre-rendered area is outside of the */
+  /* viewport but still there should remain visible area. */
+  to { transform: translateX(-150vw); }
+}
+#target {
+  width: 200vw;
+  height: 200vh;
+  position: absolute;
+  transform: translateX(0vw);
+}
+</style>
+<div id="target">
+  <!--
+    Put an SVG element so that the transform display item has a blob on
+    WebRender which means this test properly fails without the proper fix.
+    -->
+  <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 16 16">
+    <rect fill="green" width="16" height="16"></rect>
+  </svg>
+</div>
+<script>
+document.addEventListener("MozReftestInvalidate", () => {
+  target.style.animation = "anim 100s 1s step-start";
+  target.addEventListener("animationstart", () => {
+    // animtionstart event is fired just before requestAnimationFrame callbacks,
+    // so we need to wait two rAF to make sure the initial animation value is
+    // composited on the compositor.
+    requestAnimationFrame(() => {
+      requestAnimationFrame(() => {
+        document.documentElement.classList.remove("reftest-wait");
+      });
+    });
+  });
+}, { once: true });
+</script>
+</html>