diff --git a/loading/lazyload/attribute_off_iframe_cross_origin.tentative.sub.html b/loading/lazyload/attribute_off_iframe_cross_origin.tentative.sub.html
new file mode 100644
index 00000000000000..50e45f25ea5d7a
--- /dev/null
+++ b/loading/lazyload/attribute_off_iframe_cross_origin.tentative.sub.html
@@ -0,0 +1,48 @@
+<!DOCTYPE html>
+<head>
+  <title>Loading cross-origin iframes with lazyload="off"</title>
+  <link rel="author" title="Scott Little" href="mailto:sclittle@chromium.org">
+  <link rel="help" href="https://github.com/whatwg/html/pull/3752">
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+</head>
+
+<!--
+Marked as tentative until https://github.com/whatwg/html/pull/3752 is landed.
+-->
+
+<body>
+  <iframe id="in_viewport" src="https://{{hosts[][www]}}:{{ports[https][0]}}/loading/lazyload/resources/subframe_1.html" width="200px" height="100px" lazyload="off"></iframe>
+  <div style="height:10000px;"></div>
+  <iframe id="below_viewport" src="https://{{hosts[][www]}}:{{ports[https][0]}}/loading/lazyload/resources/subframe_2.html" width="200px" height="100px" lazyload="off"></iframe>
+</body>
+
+<script>
+  async_test(function(t) {
+    window.addEventListener("load", t.step_func_done());
+  }, "Test that document load event is fired");
+
+  async_test(function(t) {
+    var has_in_viewport_iframe_loaded = false;
+    document.getElementById("in_viewport").addEventListener("load",
+      t.step_func(function() {
+        assert_false(has_in_viewport_iframe_loaded);
+        has_in_viewport_iframe_loaded = true;
+      }));
+    window.addEventListener("load", t.step_func_done(function() {
+      assert_true(has_in_viewport_iframe_loaded);
+    }));
+  }, "Test that the in-viewport iframe loads immediately.");
+
+  async_test(function(t) {
+    var has_below_viewport_iframe_loaded = false;
+    document.getElementById("below_viewport").addEventListener("load",
+      t.step_func(function() {
+        assert_false(has_below_viewport_iframe_loaded);
+        has_below_viewport_iframe_loaded = true;
+      }));
+    window.addEventListener("load", t.step_func_done(function() {
+      assert_true(has_below_viewport_iframe_loaded);
+    }));
+  }, "Test that the below-viewport iframe loads immediately.");
+</script>
diff --git a/loading/lazyload/attribute_off_iframe_same_origin.tentative.html b/loading/lazyload/attribute_off_iframe_same_origin.tentative.html
new file mode 100644
index 00000000000000..f1df433f2c05ea
--- /dev/null
+++ b/loading/lazyload/attribute_off_iframe_same_origin.tentative.html
@@ -0,0 +1,48 @@
+<!DOCTYPE html>
+<head>
+  <title>Loading same-origin iframes with lazyload="off"</title>
+  <link rel="author" title="Scott Little" href="mailto:sclittle@chromium.org">
+  <link rel="help" href="https://github.com/whatwg/html/pull/3752">
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+</head>
+
+<!--
+Marked as tentative until https://github.com/whatwg/html/pull/3752 is landed.
+-->
+
+<body>
+  <iframe id="in_viewport" src="resources/subframe_1.html" width="200px" height="100px" lazyload="off"></iframe>
+  <div style="height:10000px;"></div>
+  <iframe id="below_viewport" src="resources/subframe_2.html" width="200px" height="100px" lazyload="off"></iframe>
+</body>
+
+<script>
+  async_test(function(t) {
+    window.addEventListener("load", t.step_func_done());
+  }, "Test that document load event is fired");
+
+  async_test(function(t) {
+    var has_in_viewport_iframe_loaded = false;
+    document.getElementById("in_viewport").addEventListener("load",
+      t.step_func(function() {
+        assert_false(has_in_viewport_iframe_loaded);
+        has_in_viewport_iframe_loaded = true;
+      }));
+    window.addEventListener("load", t.step_func_done(function() {
+      assert_true(has_in_viewport_iframe_loaded);
+    }));
+  }, "Test that the in-viewport iframe loads immediately.");
+
+  async_test(function(t) {
+    var has_below_viewport_iframe_loaded = false;
+    document.getElementById("below_viewport").addEventListener("load",
+      t.step_func(function() {
+        assert_false(has_below_viewport_iframe_loaded);
+        has_below_viewport_iframe_loaded = true;
+      }));
+    window.addEventListener("load", t.step_func_done(function() {
+      assert_true(has_below_viewport_iframe_loaded);
+    }));
+  }, "Test that the below-viewport iframe loads immediately.");
+</script>
diff --git a/loading/lazyload/attribute_off_image.tentative.html b/loading/lazyload/attribute_off_image.tentative.html
new file mode 100644
index 00000000000000..3af45e42548d34
--- /dev/null
+++ b/loading/lazyload/attribute_off_image.tentative.html
@@ -0,0 +1,48 @@
+<!DOCTYPE html>
+<head>
+  <title>Loading images with lazyload="off"</title>
+  <link rel="author" title="Scott Little" href="mailto:sclittle@chromium.org">
+  <link rel="help" href="https://github.com/whatwg/html/pull/3752">
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+</head>
+
+<!--
+Marked as tentative until https://github.com/whatwg/html/pull/3752 is landed.
+-->
+
+<body>
+  <img id="in_viewport" src="resources/image_1.png" lazyload="off">
+  <div style="height:10000px;"></div>
+  <img id="below_viewport" src="resources/image_2.png" lazyload="off">
+</body>
+
+<script>
+  async_test(function(t) {
+    window.addEventListener("load", t.step_func_done());
+  }, "Test that document load event is fired");
+
+  async_test(function(t) {
+    var has_in_viewport_image_loaded = false;
+    document.getElementById("in_viewport").addEventListener("load",
+      t.step_func(function() {
+        assert_false(has_in_viewport_image_loaded);
+        has_in_viewport_image_loaded = true;
+      }));
+    window.addEventListener("load", t.step_func_done(function() {
+      assert_true(has_in_viewport_image_loaded);
+    }));
+  }, "Test that the in-viewport image loads immediately.");
+
+  async_test(function(t) {
+    var has_below_viewport_image_loaded = false;
+    document.getElementById("below_viewport").addEventListener("load",
+      t.step_func(function() {
+        assert_false(has_below_viewport_image_loaded);
+        has_below_viewport_image_loaded = true;
+      }));
+    window.addEventListener("load", t.step_func_done(function() {
+      assert_true(has_below_viewport_image_loaded);
+    }));
+  }, "Test that the below-viewport image loads immediately.");
+</script>
diff --git a/loading/lazyload/resources/image_1.png b/loading/lazyload/resources/image_1.png
new file mode 100644
index 00000000000000..b712825093805d
Binary files /dev/null and b/loading/lazyload/resources/image_1.png differ
diff --git a/loading/lazyload/resources/image_2.png b/loading/lazyload/resources/image_2.png
new file mode 100644
index 00000000000000..b712825093805d
Binary files /dev/null and b/loading/lazyload/resources/image_2.png differ
diff --git a/loading/lazyload/resources/subframe_1.html b/loading/lazyload/resources/subframe_1.html
new file mode 100644
index 00000000000000..98c0cec670823a
--- /dev/null
+++ b/loading/lazyload/resources/subframe_1.html
@@ -0,0 +1,5 @@
+<html>
+  <body>
+    <p>Subframe 1.</p>
+  </body>
+</html>
diff --git a/loading/lazyload/resources/subframe_2.html b/loading/lazyload/resources/subframe_2.html
new file mode 100644
index 00000000000000..47c3c711ef5045
--- /dev/null
+++ b/loading/lazyload/resources/subframe_2.html
@@ -0,0 +1,5 @@
+<html>
+  <body>
+    <p>Subframe 2.</p>
+  </body>
+</html>
