1 files changed, 51 insertions, 0 deletions
diff --git a/dom/base/test/test_input_vsync_alignment_lower_than_normal.html b/dom/base/test/test_input_vsync_alignment_lower_than_normal.html
new file mode 100644
index 0000000000..1d06e506b4
--- /dev/null
+++ b/dom/base/test/test_input_vsync_alignment_lower_than_normal.html
@@ -0,0 +1,51 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <script src="/tests/SimpleTest/SimpleTest.js"></script>
+  <script src="/tests/SimpleTest/EventUtils.js"></script>
+  <link rel="stylesheet" href="/tests/SimpleTest/test.css">
+</head>
+<body >
+  <script type="text/javascript">
+  SimpleTest.waitForExplicitFinish();
+
+  let runOrder = [];
+  function checkResult() {
+    if (runOrder.length == 3) {
+      if (runOrder[0] === "Normal") {
+        isDeeply(
+            runOrder,
+            ["Normal", "InputHigh", "Vsync"],
+            "Input priority tasks should let normal tasks to run first when there's no pending vsync"
+        );
+        SimpleTest.finish();
+      } else {
+        runOrder = [];
+        runTest();
+      }
+    }
+  }
+
+  function runTest() {
+    window.requestAnimationFrame(() => {
+      window.requestAnimationFrame(() => {
+        runOrder.push("Vsync");
+        checkResult();
+      });
+      SpecialPowers.Services.tm.dispatchToMainThread(function() {
+        runOrder.push("InputHigh");
+        checkResult();
+      }, SpecialPowers.Ci.nsIRunnablePriority.PRIORITY_INPUT_HIGH);
+      SpecialPowers.Services.tm.dispatchToMainThread(function() {
+        runOrder.push("Normal");
+        checkResult();
+      }, SpecialPowers.Ci.nsIRunnablePriority.PRIORITY_NORMAL);
+    });
+  }
+
+  SpecialPowers.pushPrefEnv({
+      set: [["dom.input_events.strict_input_vsync_alignment", true]]
+  }, runTest());
+  </script>
+</body>
+</html>