1 files changed, 110 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html b/testing/web-platform/tests/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html
new file mode 100644
index 0000000000..336703ebc4
--- /dev/null
+++ b/testing/web-platform/tests/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy.html
@@ -0,0 +1,110 @@
+<!DOCTYPE html>
+<head>
+  <title>Iframes with loading='lazy' load when in the viewport</title>
+  <link rel="author" title="Scott Little" href="mailto:sclittle@chromium.org">
+  <link rel="author" title="Dom Farolino" href="mailto:dom@chromium.org">
+  <link rel="help" href="https://github.com/whatwg/html/pull/5579">
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+</head>
+
+<script>
+  const t_in_viewport =
+    async_test('In-viewport iframes load eagerly');
+  const t_below_viewport =
+    async_test('Below-viewport iframes load lazily');
+  const t_below_viewport_srcdoc =
+    async_test('Below-viewport srcdoc iframes load lazily');
+  const t_below_viewport_data_url =
+    async_test('Below-viewport data: url iframes load lazily');
+  const t_below_viewport_blob_url =
+    async_test('Below-viewport blob url iframes load lazily');
+
+
+  document.addEventListener('DOMContentLoaded', e => {
+    const blob_url_iframe = document.querySelector('#below_viewport_blob_url');
+    const blob = new Blob(['<p>Blob subframe</p>'], {type: 'text/html'});
+    const url = URL.createObjectURL(blob);
+    blob_url_iframe.src = url;
+  });
+
+  let has_window_loaded = false;
+
+  const in_viewport_iframe_onload = t_in_viewport.step_func_done(() => {
+    assert_false(has_window_loaded,
+      "The in_viewport iframe should not block the load event");
+  });
+
+  window.addEventListener("load", () => {
+    has_window_loaded = true;
+    document.getElementById("below_viewport_srcdoc").scrollIntoView();
+  });
+
+  const below_viewport_iframe_onload = t_below_viewport.step_func_done(() => {
+    assert_true(has_window_loaded,
+                "The window load event should have fired before " +
+                "the below-viewport iframe loads");
+  });
+
+  // Onload handlers for below-viewport srcdoc iframe.
+  // Must make this accessible to the srcdoc iframe's body.
+  window.below_viewport_srcdoc_iframe_subresource_onload = t_below_viewport_srcdoc.step_func(() => {
+    assert_true(has_window_loaded,
+                "The window load event should have fired before " +
+                "the below-viewport srcdoc iframe's subresource loads");
+  });
+
+  const below_viewport_srcdoc_iframe_onload = t_below_viewport_srcdoc.step_func_done(() => {
+    assert_true(has_window_loaded,
+                "The window load event should have fired before " +
+                "the below-viewport srcdoc iframe loads");
+  });
+
+  // Onload handler for below-viewport data url iframe.
+  const below_viewport_data_url_iframe_onload = t_below_viewport_data_url.step_func_done(() => {
+    assert_true(has_window_loaded,
+                "The window load event should have fired before " +
+                "the below-viewport data url iframe loads");
+  });
+
+  // Onload handler for below-viewport blob url iframe.
+  const below_viewport_blob_url_iframe_onload = t_below_viewport_blob_url.step_func_done(() => {
+    assert_true(has_window_loaded,
+                "The window load event should have fired before " +
+                "the below-viewport blob url iframe loads");
+  });
+
+</script>
+
+<body>
+  <iframe id="in_viewport" src="resources/subframe.html?in-viewport"
+          loading="lazy" width="200px" height="100px"
+          onload="in_viewport_iframe_onload();"></iframe>
+
+  <div style="height:2000vh;"></div>
+  <iframe id="below_viewport" src="resources/subframe.html?below-viewport"
+          loading="lazy" width="200px" height="100px"
+          onload="below_viewport_iframe_onload();"></iframe>
+  <iframe id="below_viewport_srcdoc"
+          srcdoc="<body><img src='/common/square.png?below-viewport'
+                  onload='parent.below_viewport_srcdoc_iframe_subresource_onload();'></body>"
+          loading="lazy" width="200px" height="100px"
+          onload="below_viewport_srcdoc_iframe_onload();"></iframe>
+  <iframe id="below_viewport_data_url"
+          src="data:text/html,<p>Subframe</p>"
+          loading="lazy" width="200px" height="100px"
+          onload="below_viewport_data_url_iframe_onload();"></iframe>
+  <!-- This iframe has its `src` set to a blob URL dynamically above -->
+  <iframe id="below_viewport_blob_url"
+          loading="lazy" width="200px" height="100px"
+          onload="below_viewport_blob_url_iframe_onload();"></iframe>
+
+
+
+  <!-- This async script loads very slowly in order to ensure that, if the
+       below_viewport* elements have started loading, it has a chance to finish
+       loading before window load event fires, so that the test will dependably
+       fail in that case instead of potentially passing depending on how long
+       different resource fetches take. -->
+  <script async src="/common/slow.py"></script>
+</body>