diff --git a/tests/wpt/metadata/MANIFEST.json b/tests/wpt/metadata/MANIFEST.json
index 1e7fbf4dab8..806d5061874 100644
--- a/tests/wpt/metadata/MANIFEST.json
+++ b/tests/wpt/metadata/MANIFEST.json
@@ -277968,6 +277968,9 @@
    "lint.whitelist": [
     []
    ],
+   "loading/lazyload/META.yml": [
+    []
+   ],
    "loading/lazyload/common.js": [
     []
    ],
@@ -373157,6 +373160,18 @@
      {}
     ]
    ],
+   "loading/lazyload/original-base-url-applied-2-tentative.html": [
+    [
+     "loading/lazyload/original-base-url-applied-2-tentative.html",
+     {}
+    ]
+   ],
+   "loading/lazyload/original-base-url-applied-iframe-tentative.html": [
+    [
+     "loading/lazyload/original-base-url-applied-iframe-tentative.html",
+     {}
+    ]
+   ],
    "loading/lazyload/original-base-url-applied-tentative.html": [
     [
      "loading/lazyload/original-base-url-applied-tentative.html",
@@ -668530,12 +668545,16 @@
    "d06f4c59bca28d01632cf693062a7d30ecbd5cc8",
    "support"
   ],
+  "loading/lazyload/META.yml": [
+   "cf46037be689ed345755b4c14fc76ae0a9951e8e",
+   "support"
+  ],
   "loading/lazyload/common.js": [
    "06f18b3e0498549df1811c6a8008857e65b4117c",
    "support"
   ],
   "loading/lazyload/disconnected-image-loading-lazy.tentative.html": [
-   "c3b72b26239ea18c0575b65d0d6aa3aaef08792d",
+   "fe6d79fe2a558bae6740932e24ff31c30425225c",
    "testharness"
   ],
   "loading/lazyload/iframe-loading-eager.tentative.html": [
@@ -668563,7 +668582,15 @@
    "testharness"
   ],
   "loading/lazyload/invisible-lazy-image.tentative.html": [
-   "805d614e401670a5d73199a6771a028a7e41d7d6",
+   "94f0dbfd6da8178119f51e3be29f77869e46da22",
+   "testharness"
+  ],
+  "loading/lazyload/original-base-url-applied-2-tentative.html": [
+   "debfbadb2b04fc462f8cee0cd1579bf7a8096157",
+   "testharness"
+  ],
+  "loading/lazyload/original-base-url-applied-iframe-tentative.html": [
+   "0734b335781629c4084d6e9646a61d9b80017169",
    "testharness"
   ],
   "loading/lazyload/original-base-url-applied-tentative.html": [
diff --git a/tests/wpt/metadata/fetch/content-type/response.window.js.ini b/tests/wpt/metadata/fetch/content-type/response.window.js.ini
index 254d9678e47..3d77dd6fefc 100644
--- a/tests/wpt/metadata/fetch/content-type/response.window.js.ini
+++ b/tests/wpt/metadata/fetch/content-type/response.window.js.ini
@@ -309,9 +309,24 @@
   [<iframe>: separate response Content-Type: */* text/html]
     expected: FAIL
 
-  [<iframe>: combined response Content-Type: text/html;" text/plain]
+  [<iframe>: combined response Content-Type: */* text/html]
     expected: FAIL
 
-  [<iframe>: combined response Content-Type: text/html;" \\" text/plain]
+  [<iframe>: separate response Content-Type: text/html;" text/plain]
+    expected: FAIL
+
+  [<iframe>: separate response Content-Type: text/html */*;charset=gbk]
+    expected: FAIL
+
+  [<iframe>: separate response Content-Type: text/html */*]
+    expected: FAIL
+
+  [<iframe>: separate response Content-Type: text/plain */*]
+    expected: FAIL
+
+  [<iframe>: separate response Content-Type: text/html;x=" text/plain]
+    expected: FAIL
+
+  [<iframe>: combined response Content-Type: text/html;x=" text/plain]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini b/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini
index cea868999e8..a639f15230c 100644
--- a/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini
+++ b/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini
@@ -14,6 +14,3 @@
   [Content-Type-Options%3A%20nosniff]
     expected: FAIL
 
-  [X-Content-Type-Options%3A%20%40%23%24%23%25%25%26%5E%26%5E*()()11!%2Cnosniff]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_1.html.ini b/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_1.html.ini
deleted file mode 100644
index 87b07c3e670..00000000000
--- a/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_1.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[traverse_the_history_1.html]
-  [Multiple history traversals from the same task]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_5.html.ini b/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_4.html.ini
similarity index 71%
rename from tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_5.html.ini
rename to tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_4.html.ini
index dc2e45516de..385376c7321 100644
--- a/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_5.html.ini
+++ b/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_4.html.ini
@@ -1,4 +1,4 @@
-[traverse_the_history_5.html]
+[traverse_the_history_4.html]
   [Multiple history traversals, last would be aborted]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/skip-document-with-fragment.html.ini b/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/skip-document-with-fragment.html.ini
index 6852d7663de..c12c0f8ae48 100644
--- a/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/skip-document-with-fragment.html.ini
+++ b/tests/wpt/metadata/html/interaction/focus/the-autofocus-attribute/skip-document-with-fragment.html.ini
@@ -1,8 +1,4 @@
 [skip-document-with-fragment.html]
-  expected: TIMEOUT
   [Autofocus elements in iframed documents with URL fragments should be skipped.]
     expected: FAIL
 
-  [Autofocus elements in top-level browsing context's documents with URI fragments should be skipped.]
-    expected: TIMEOUT
-
diff --git a/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-3.html.ini b/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-3.html.ini
index 2568040e6e5..e440b1e38c6 100644
--- a/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-3.html.ini
+++ b/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-3.html.ini
@@ -1,6 +1,6 @@
 [iframe_sandbox_popups_nonescaping-3.html]
   type: testharness
-  expected: CRASH
+  expected: TIMEOUT
   [Check that popups from a sandboxed iframe do not escape the sandbox]
-    expected: FAIL
+    expected: NOTRUN
 
diff --git a/tests/wpt/metadata/html/semantics/scripting-1/the-script-element/script-onerror-insertion-point-2.html.ini b/tests/wpt/metadata/html/semantics/scripting-1/the-script-element/script-onerror-insertion-point-2.html.ini
deleted file mode 100644
index 178680e5d14..00000000000
--- a/tests/wpt/metadata/html/semantics/scripting-1/the-script-element/script-onerror-insertion-point-2.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[script-onerror-insertion-point-2.html]
-  expected: TIMEOUT
diff --git a/tests/wpt/metadata/resource-timing/crossorigin-sandwich-TAO.sub.html.ini b/tests/wpt/metadata/resource-timing/crossorigin-sandwich-TAO.sub.html.ini
index b4090ef9fe2..1c7ec9ce1db 100644
--- a/tests/wpt/metadata/resource-timing/crossorigin-sandwich-TAO.sub.html.ini
+++ b/tests/wpt/metadata/resource-timing/crossorigin-sandwich-TAO.sub.html.ini
@@ -1,5 +1,4 @@
 [crossorigin-sandwich-TAO.sub.html]
-  expected: ERROR
   [There should be one entry.]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/webmessaging/without-ports/017.html.ini b/tests/wpt/metadata/webmessaging/without-ports/017.html.ini
new file mode 100644
index 00000000000..064cf47545b
--- /dev/null
+++ b/tests/wpt/metadata/webmessaging/without-ports/017.html.ini
@@ -0,0 +1,5 @@
+[017.html]
+  expected: TIMEOUT
+  [origin of the script that invoked the method, about:blank]
+    expected: TIMEOUT
+
diff --git a/tests/wpt/web-platform-tests/loading/lazyload/META.yml b/tests/wpt/web-platform-tests/loading/lazyload/META.yml
new file mode 100644
index 00000000000..cf46037be68
--- /dev/null
+++ b/tests/wpt/web-platform-tests/loading/lazyload/META.yml
@@ -0,0 +1,4 @@
+spec: https://github.com/whatwg/html/pull/3752
+suggested_reviewers:
+  - domfarolino
+  - rwlbuis
diff --git a/tests/wpt/web-platform-tests/loading/lazyload/disconnected-image-loading-lazy.tentative.html b/tests/wpt/web-platform-tests/loading/lazyload/disconnected-image-loading-lazy.tentative.html
index c3b72b26239..fe6d79fe2a5 100644
--- a/tests/wpt/web-platform-tests/loading/lazyload/disconnected-image-loading-lazy.tentative.html
+++ b/tests/wpt/web-platform-tests/loading/lazyload/disconnected-image-loading-lazy.tentative.html
@@ -3,28 +3,30 @@
 <script src="/resources/testharnessreport.js"></script>
 <body>
 <script>
-async_test(function(t) {
+async_test(t => {
   x = new Image();
   x.loading = "auto";
   x.src = "resources/image.png?auto";
-  x.onload = e => {
-    t.step(function() {
-      t.step_func_done();
-    });
-  };
-  t.step_timeout(function() { t.done(); }, 2000);
+  x.onload = t.step_func_done();
+  t.step_timeout(t.unreached_func("Disconnected loading=auto image loads " +
+                                  "successfully, and doesn't timeout"), 2000);
 }, "loading=auto for disconnected image");
 
-async_test(function(t) {
+async_test(t => {
+  x = new Image();
+  x.loading = "eager";
+  x.src = "resources/image.png?eager";
+  x.onload = t.step_func_done();
+  t.step_timeout(t.unreached_func("Disconnected loading=eager image loads " +
+                                  "successfully, and doesn't timeout"), 2000);
+}, "loading=eager for disconnected image");
+
+async_test(t => {
   x = new Image();
   x.loading = "lazy";
   x.src = "resources/image.png?lazy";
-  x.onload = e => {
-    t.step(function() {
-      t.unreached_func("Disconnected image with loading=lazy should be loaded lazily.");
-    });
-  };
-  t.step_timeout(function() { t.done(); }, 2000);
+  x.onload = t.unreached_func("Disconnected loading=lazy image loads lazily.");
+  t.step_timeout(t.step_func_done(), 2000);
 }, "loading=lazy for disconnected image");
 </script>
 </body>
diff --git a/tests/wpt/web-platform-tests/loading/lazyload/invisible-lazy-image.tentative.html b/tests/wpt/web-platform-tests/loading/lazyload/invisible-lazy-image.tentative.html
index 805d614e401..94f0dbfd6da 100644
--- a/tests/wpt/web-platform-tests/loading/lazyload/invisible-lazy-image.tentative.html
+++ b/tests/wpt/web-platform-tests/loading/lazyload/invisible-lazy-image.tentative.html
@@ -8,16 +8,19 @@
 </head>
 
 <body>
-  <img id="expected" src='resources/image.png?1'>
+  <!-- These two images should load, the latter not blocking the window load event -->
+  <img id="expected" src='resources/image.png?expected&pipe=trickle(d1)'>
   <img id="visibility_hidden" style="visibility:hidden;"
-       src='resources/image.png?2&pipe=trickle(d1)' loading='lazy'
+       src='resources/image.png?visibility_hidden&pipe=trickle(d2)' loading='lazy'
        onload="visibility_hidden_img.resolve();" onerror="visibility_hidden_img.reject();">
-  <img id="display_none" style="display:none;" src='resources/image.png?3&pipe=trickle(d1)'
+
+  <!-- These images should not load at all -->
+  <img id="display_none" style="display:none;" src='resources/image.png?display_none'
        loading='lazy'
        onload="display_none_img.resolve();" onerror="display_none_img.reject();">
-  <img id="attribute_hidden" hidden src='resources/image.png?4&pipe=trickle(d1)' loading='lazy'
+  <img id="attribute_hidden" hidden src='resources/image.png?attribute_hidden' loading='lazy'
        onload="attribute_hidden_img.resolve();" onerror="attribute_hidden_img.reject();">
-  <img id="js_display_none" src='resources/image.png?5&pipe=trickle(d1)' loading='lazy'
+  <img id="js_display_none" src='resources/image.png?js_display_none' loading='lazy'
        onload="js_display_none_img.resolve();" onerror="js_display_none_img.reject();">
   <script>
     document.getElementById("js_display_none").style = 'display:none;';
@@ -37,31 +40,39 @@ Marked as tentative until https://github.com/whatwg/html/pull/3752 is landed.
 
   let has_window_loaded = false;
 
-  async_test(function(t) {
-    window.addEventListener("load", t.step_func(function() {
+  async_test(t => {
+    window.addEventListener("load", t.step_func(() => {
       has_window_loaded = true;
     }));
 
-    display_none_img.promise.then(
-      t.unreached_func("The lazy image with display:none should not load since it is hidden.")
-    ).catch(t.unreached_func("The error event should not fire for lazy images with display none."));
+    const unreached_not_rendered_img_func =
+      t.unreached_func("The not-rendered in-viewport loading=lazy images " +
+                       "should not have attempted to load.");
 
-    attribute_hidden_img.promise.then(
-      t.unreached_func("The lazy image with attribute hidden should not load since it is hidden.")
-    ).catch(t.unreached_func("The error event should not fire for lazy image with attribute hidden."));
+    display_none_img.promise
+      .then(unreached_not_rendered_img_func)
+      .catch(unreached_not_rendered_img_func);
 
-    js_display_none_img.promise.then(
-      t.unreached_func("The lazy image with display:none set by JS should not load since it is hidden.")
-    ).catch(t.unreached_func("The error event should not fire for lazy image with display none set by JS."));
+    attribute_hidden_img.promise
+      .then(unreached_not_rendered_img_func)
+      .catch(unreached_not_rendered_img_func);
+
+    js_display_none_img.promise
+      .then(unreached_not_rendered_img_func)
+      .catch(unreached_not_rendered_img_func);
 
     visibility_hidden_img.promise.then(
-      t.step_func(function() {
-        assert_true(is_image_fully_loaded(visibility_hidden_img.element(),
-                                          expected));
-        assert_true(has_window_loaded);
-        t.step_timeout(function() { t.done(); }, 2000);
+      t.step_func_done(() => {
+        assert_true(is_image_fully_loaded(visibility_hidden_img.element(), expected),
+                    "The loading=lazy visibility:hidden image is equivalent " +
+                    "to the expected image.");
+        assert_true(has_window_loaded,
+                    "The loading=lazy visibility:hidden image does not block " +
+                    "the window load event, and finishes loading after the " +
+                    "window load event fires.");
       })
-    ).catch(t.unreached_func("The error event should not fire for lazy image with visibility hidden."));
+    ).catch(t.unreached_func("The loading=lazy visibility:hidden image " +
+                             "should load successfully."));
   }, "Test behavior of in viewport invisible lazy images");
 </script>
 
diff --git a/tests/wpt/web-platform-tests/loading/lazyload/original-base-url-applied-2-tentative.html b/tests/wpt/web-platform-tests/loading/lazyload/original-base-url-applied-2-tentative.html
new file mode 100644
index 00000000000..debfbadb2b0
--- /dev/null
+++ b/tests/wpt/web-platform-tests/loading/lazyload/original-base-url-applied-2-tentative.html
@@ -0,0 +1,55 @@
+<!DOCTYPE html>
+<head>
+  <title>Deferred images with loading='lazy' use the original
+         base URL specified at the parse time</title>
+  <link rel="author" title="Rob Buis" href="mailto:rbuis@igalia.com">
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="common.js"></script>
+  <base href='/loading/lazyload/resources/'>
+</head>
+
+<!--
+Marked as tentative until https://github.com/whatwg/html/pull/3752 is landed.
+-->
+
+<script>
+  const below_viewport_img_promise = new ElementLoadPromise("below_viewport_img");
+
+  let has_window_loaded = false;
+
+  async_test(function(t) {
+
+    // Change the base URL and scroll down to load the deferred elements.
+    window.addEventListener("load", t.step_func(function() {
+      const base = document.getElementsByTagName('base')[0];
+      base.href = '/invalid-url-where-no-subresources-exist/';
+      has_window_loaded = true;
+      below_viewport_img_promise.element().scrollIntoView();
+    }));
+
+    below_viewport_img_promise.promise.then(
+      t.step_func_done(function() {
+        assert_true(has_window_loaded,
+                    "Below-viewport loading=lazy images do not block the " +
+                    "window load event");
+        assert_true(below_viewport_img_promise.element().complete,
+                    "The loading=lazy image should be considered complete " +
+                    "upon load.");
+        assert_greater_than(below_viewport_img_promise.element().naturalWidth,
+                            0,
+                            "The loading=lazy should have non-zero width " +
+                            "upon loading");
+      })
+    ).catch(t.unreached_func("The image request should not load relative to " +
+                             "the current (incorrect) base URL."));
+  }, "Deferred images with loading='lazy' use the original base URL " +
+     "specified at the parse time");
+</script>
+
+<body>
+  <div style="height:1000vh"></div>
+  <img id="below_viewport_img" src="image.png" loading="lazy"
+       onload="below_viewport_img_promise.resolve();"
+       onerror="below_viewport_img_promise.reject();">
+</body>
diff --git a/tests/wpt/web-platform-tests/loading/lazyload/original-base-url-applied-iframe-tentative.html b/tests/wpt/web-platform-tests/loading/lazyload/original-base-url-applied-iframe-tentative.html
new file mode 100644
index 00000000000..0734b335781
--- /dev/null
+++ b/tests/wpt/web-platform-tests/loading/lazyload/original-base-url-applied-iframe-tentative.html
@@ -0,0 +1,53 @@
+<!DOCTYPE html>
+<head>
+  <title>Deferred iframes with loading='lazy' use the original
+         base URL specified at the parse time</title>
+  <link rel="author" title="Rob Buis" href="mailto:rbuis@igalia.com">
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="common.js"></script>
+  <base href='/loading/lazyload/resources/'>
+</head>
+
+<!--
+Marked as tentative until Marked as tentative until the HTML Standard
+specifies this.
+-->
+
+<script>
+  const below_viewport_iframe_promise = new ElementLoadPromise("below_viewport_iframe");
+
+  let has_window_loaded = false;
+
+  async_test(function(t) {
+
+    // Change the base URL and scroll down to load the deferred elements.
+    window.addEventListener("load", t.step_func(function() {
+      const base = document.getElementsByTagName('base')[0];
+      base.href = '/invalid-url-where-no-subresources-exist/';
+      has_window_loaded = true;
+      below_viewport_iframe_promise.element().scrollIntoView();
+    }));
+
+    below_viewport_iframe_promise.promise.then(
+      t.step_func_done(function() {
+        assert_true(has_window_loaded,
+                    "Below-viewport loading=lazy iframes do not block the " +
+                    "window load event");
+        assert_true(below_viewport_iframe_promise.element().contentDocument.body.
+                    innerHTML.includes("<p>Subframe</p>"),
+                    "The loading=lazy iframe's content is accessible upon loading");
+      })
+    ).catch(t.unreached_func("The iframe request should not load relative to " +
+                             "the current (incorrect) base URL."));
+  }, "Deferred iframes with loading='lazy' use the original base URL " +
+      "specified at the parse time");
+</script>
+
+<body>
+  <div style="height:1000vh"></div>
+  <iframe id="below_viewport_iframe" src="subframe.html" loading="lazy"
+    width="200px" height="100px" onload="below_viewport_iframe_promise.resolve();"
+    onerror="below_viewport_iframe_promise.reject();">
+  </iframe>
+</body>