1 files changed, 30 insertions, 0 deletions
diff --git a/testing/web-platform/tests/hr-time/resources/clamped-time-origin.js b/testing/web-platform/tests/hr-time/resources/clamped-time-origin.js
new file mode 100644
index 0000000000..09967ed6d1
--- /dev/null
+++ b/testing/web-platform/tests/hr-time/resources/clamped-time-origin.js
@@ -0,0 +1,30 @@
+const run_test = isolated => {
+  // Multiplier to convert the clamped timestamps to microseconds.
+  const multiplier = 1000;
+  const windowOrigin = performance.timeOrigin;
+  // Clamp to at least 5 microseconds in isolated contexts and at least 100 in
+  // non-isolated ones.
+  const resolution = isolated ? 5 : 100;
+
+  const create_worker = () => {
+    return new Promise(resolve => {
+      const workerScript = 'postMessage({timeOrigin: performance.timeOrigin})';
+      const blob = new Blob([workerScript]);
+      const worker = new Worker(URL.createObjectURL(blob));
+      worker.addEventListener('message', event => {
+        resolve(event.data.timeOrigin);
+      });
+    });
+  };
+  promise_test(async t => {
+    assert_equals(self.crossOriginIsolated, isolated,
+      "crossOriginIsolated is properly set");
+    let prev = windowOrigin;
+    let current;
+    for (let i = 1; i < 100; ++i) {
+      current = await create_worker();
+      assert_true(current === prev || current - prev > resolution / 1000);
+      prev = current;
+    }
+  }, 'timeOrigins are clamped.');
+};