1 files changed, 36 insertions, 0 deletions
diff --git a/testing/web-platform/tests/element-timing/cross-origin-iframe-element.sub.html b/testing/web-platform/tests/element-timing/cross-origin-iframe-element.sub.html
new file mode 100644
index 0000000000..2f49933ab9
--- /dev/null
+++ b/testing/web-platform/tests/element-timing/cross-origin-iframe-element.sub.html
@@ -0,0 +1,36 @@
+<!DOCTYPE HTML>
+<meta charset=utf-8>
+<title>Element Timing: do NOT observe elements from cross-origin iframes</title>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="resources/element-timing-helpers.js"></script>
+<script>
+  async_test((t) => {
+    assert_implements(window.PerformanceElementTiming, "PerformanceElementTiming is not implemented");
+    const observer = new PerformanceObserver(
+      t.step_func_done((entryList) => {
+        assert_unreached("We should not observe a cross origin element.");
+      })
+    );
+    observer.observe({entryTypes: ['element']});
+    // We add the iframe during onload to be sure that the observer is registered
+    // in time for it to observe the element timing.
+    // TODO(npm): change observer to use buffered flag.
+    window.onload = t.step_func(() => {
+      // Add a cross origin iframe with an image.
+      const iframe = document.createElement('iframe');
+      iframe.src = 'http://{{domains[www]}}:{{ports[http][1]}}'
+          + '/element-timing/resources/iframe-with-square.html';
+      document.body.appendChild(iframe);
+      iframe.onload = t.step_func(() => {
+        t.step_timeout( () => {
+          // After some wait, assume observer did not receive the entry, so the test passes.
+          t.done();
+        }, 100);
+      });
+    });
+  }, 'Element from cross origin iframe is NOT observable.');
+</script>
+
+</body>