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diff --git a/testing/web-platform/tests/html/semantics/embedded-content/the-img-element/image-loading-lazy.html b/testing/web-platform/tests/html/semantics/embedded-content/the-img-element/image-loading-lazy.html
new file mode 100644
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+++ b/testing/web-platform/tests/html/semantics/embedded-content/the-img-element/image-loading-lazy.html
@@ -0,0 +1,112 @@
+<!DOCTYPE html>
+<head>
+  <title>Images with loading='lazy' load only when in the viewport</title>
+  <link rel="author" title="Dom Farolino" href="mailto:dom@chromium.org">
+  <link rel="author" title="Scott Little" href="mailto:sclittle@chromium.org">
+  <link rel="help" href="https://github.com/scott-little/lazyload">
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+</head>
+
+<script>
+  const in_viewport_test =
+    async_test("In-viewport loading=lazy images load immediately but do not " +
+               "block the window load event");
+  const below_viewport_test =
+    async_test("Below-viewport loading=lazy images only load when in the " +
+               "viewport and do not block the window load event");
+  const below_viewport_data_url_test =
+    async_test("Below-viewport data:url images only load when in the " +
+               "viewport and do not block the window load event");
+  const below_viewport_blob_url_test =
+    async_test("Below-viewport blob URL images only load when in the " +
+               "viewport and do not block the window load event");
+
+  document.addEventListener('DOMContentLoaded', e => {
+    const img = document.querySelector('#below_viewport_blob_url');
+
+    // Blob URL helper.
+    // Source: https://bl.ocks.org/nolanlawson/0eac306e4dac2114c752.
+    function fixBinary(bin) {
+      const length = bin.length;
+      const buf = new ArrayBuffer(length);
+      const arr = new Uint8Array(buf);
+      for (var i = 0; i < length; i++) {
+        arr[i] = bin.charCodeAt(i);
+      }
+
+      return buf;
+    }
+
+    const base64 =
+      "R0lGODlhDAAMAKIFAF5LAP/zxAAAANyuAP/gaP///wAAAAAAACH5BAEAAAUALAAAAAAMAAwAAAMlWLPcGjDKFYi9lxKBOaGcF35DhWHamZUW0K4mAbiwWtuf0uxFAgA";
+    const binary = fixBinary(atob(base64));
+    const blob = new Blob([binary], {type: 'image/png'});
+    const url = URL.createObjectURL(blob);
+    img.src = url;
+  }) // DOMContentLoaded.
+
+  let has_window_load_fired = false;
+  let has_in_viewport_loaded = false;
+
+  window.onload = e => {
+    has_window_load_fired = true;
+  }
+
+  // Helper assertion messages for the below tests.
+  const kScrollAssertion = "images only load when scrolled into view";
+  const kWindowLoadAssertion = "images do not block the load event";
+
+  const in_viewport_img_onload = in_viewport_test.step_func_done(() => {
+    has_in_viewport_loaded = true;
+    document.querySelector('#bottom').scrollIntoView();
+    assert_true(has_window_load_fired,
+                "In-viewport loading=lazy images do not block the window " +
+                "load event");
+  });
+
+  const below_viewport_img_onload = below_viewport_test.step_func_done(() => {
+    assert_true(has_in_viewport_loaded,
+                "Below-viewport loading=lazy images only load once loaded " +
+                "into the viewport");
+    assert_true(has_window_load_fired,
+                "Below-viewport loading=lazy images should not block the " +
+                "window load event");
+  });
+
+  const below_viewport_data_url_img_onload = below_viewport_data_url_test.step_func_done(() => {
+    assert_true(has_in_viewport_loaded,
+                "Below-viewport loading=lazy data: url images " +
+                kScrollAssertion);
+    assert_true(has_window_load_fired,
+                "Below-viewport loading=lazy data: url images " +
+                kWindowLoadAssertion);
+  });
+
+  const below_viewport_blob_url_img_onload = below_viewport_blob_url_test.step_func_done(() => {
+    assert_true(has_in_viewport_loaded,
+                "Below-viewport loading=lazy blob url images " +
+                kScrollAssertion);
+    assert_true(has_window_load_fired,
+                "Below-viewport loading=lazy blob url images " +
+                kWindowLoadAssertion);
+  });
+</script>
+
+<body>
+  <!-- |in_viewport| takes 2 seconds to load, so that in browsers that don't
+       support lazy loading, |below_viewport| finishes before |in_viewport|, and
+       the test will dependably fail without relying on a timeout. -->
+  <img id="in_viewport" loading="lazy" src="resources/image.png?image-loading-lazy-first&pipe=trickle(d2)"
+       onload="in_viewport_img_onload()">
+  <div style="height:1000vh;"></div>
+  <img id="below_viewport" loading="lazy" src="resources/image.png?image-loading-lazy-second"
+       onload="below_viewport_img_onload()">
+  <img id="below_viewport_data_url" loading="lazy"
+       src="data:image/png;base64,R0lGODlhDAAMAKIFAF5LAP/zxAAAANyuAP/gaP///wAAAAAAACH5BAEAAAUALAAAAAAMAAwAAAMlWLPcGjDKFYi9lxKBOaGcF35DhWHamZUW0K4mAbiwWtuf0uxFAgA"
+       onload="below_viewport_data_url_img_onload()">
+  <!-- This image has its `src` set to a blob URL dynamically above -->
+  <img id="below_viewport_blob_url" loading="lazy"
+       onload="below_viewport_blob_url_img_onload()">
+  <div id="bottom"></div>
+</body>