1 files changed, 28 insertions, 0 deletions
diff --git a/layout/reftests/web-animations/stacking-context-opacity-changing-keyframe.html b/layout/reftests/web-animations/stacking-context-opacity-changing-keyframe.html
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index 0000000000..44676d9199
--- /dev/null
+++ b/layout/reftests/web-animations/stacking-context-opacity-changing-keyframe.html
@@ -0,0 +1,28 @@
+<!DOCTYPE html>
+<html class="reftest-wait reftest-no-flush">
+<title>Changing keyframes to opacity frames creates a stacking context</title>
+<style>
+span {
+  height: 100px;
+  width: 100px;
+  position: fixed;
+  background: green;
+  top: 50px;
+}
+#test {
+  width: 100px; height: 100px;
+  background: blue;
+}
+</style>
+<span></span>
+<div id="test"></div>
+<script>
+  var anim = document.getElementById("test")
+    .animate({ }, { duration: 100000 });
+  anim.ready.then(function() {
+    anim.effect.setKeyframes({ opacity: [1, 1] });
+    requestAnimationFrame(function() {
+      document.documentElement.classList.remove("reftest-wait");
+    });
+  });
+</script>