diff --git a/tests/wpt/metadata/FileAPI/url/url-in-tags-revoke.window.js.ini b/tests/wpt/metadata/FileAPI/url/url-in-tags-revoke.window.js.ini
index 76b398963ae..a9e46713244 100644
--- a/tests/wpt/metadata/FileAPI/url/url-in-tags-revoke.window.js.ini
+++ b/tests/wpt/metadata/FileAPI/url/url-in-tags-revoke.window.js.ini
@@ -7,7 +7,7 @@
     expected: FAIL
 
   [Opening a blob URL in a new window immediately before revoking it works.]
-    expected: FAIL
+    expected: TIMEOUT
 
   [Opening a blob URL in a noopener about:blank window immediately before revoking it works.]
     expected: FAIL
diff --git a/tests/wpt/metadata/MANIFEST.json b/tests/wpt/metadata/MANIFEST.json
index 99a4907821f..81bfc918c14 100644
--- a/tests/wpt/metadata/MANIFEST.json
+++ b/tests/wpt/metadata/MANIFEST.json
@@ -264669,7 +264669,7 @@
    "docs/writing-tests/test-templates.md": [
     []
    ],
-   "docs/writing-tests/testdriver-tutorial.md": [
+   "docs/writing-tests/testdriver-extension-tutorial.md": [
     []
    ],
    "docs/writing-tests/testdriver.md": [
@@ -321772,9 +321772,15 @@
      {}
     ]
    ],
-   "css/css-masking/animations/clip-path-interpolation.html": [
+   "css/css-masking/animations/clip-path-interpolation-001.html": [
     [
-     "css/css-masking/animations/clip-path-interpolation.html",
+     "css/css-masking/animations/clip-path-interpolation-001.html",
+     {}
+    ]
+   ],
+   "css/css-masking/animations/clip-path-interpolation-002.html": [
+    [
+     "css/css-masking/animations/clip-path-interpolation-002.html",
      {}
     ]
    ],
@@ -579051,10 +579057,14 @@
    "322ebd724e8524e85d8afe369b6bafaabbec8c79",
    "testharness"
   ],
-  "css/css-masking/animations/clip-path-interpolation.html": [
+  "css/css-masking/animations/clip-path-interpolation-001.html": [
    "21c34f1f2b75ec7345a97b00db62a49b038cf026",
    "testharness"
   ],
+  "css/css-masking/animations/clip-path-interpolation-002.html": [
+   "e00170ed331bcbca450a4de5ef41c415cc88d2b9",
+   "testharness"
+  ],
   "css/css-masking/clip-path-svg-content/clip-path-clip-nested-twice.svg": [
    "269e8feed2d3c21774a7c94729c3551899ce4d92",
    "reftest"
@@ -631176,7 +631186,7 @@
    "support"
   ],
   "docs/running-tests/from-local-system.md": [
-   "0f337176c47d7c38bcaebd85fd86628e1870dfae",
+   "bc8b50ffd104199c3489415119e1ef148723827a",
    "support"
   ],
   "docs/running-tests/from-web.md": [
@@ -631236,7 +631246,7 @@
    "support"
   ],
   "docs/writing-tests/index.md": [
-   "0e0d3f35b00a20345d319914344bf779d4016aa8",
+   "84735b5ba3644a7a9e30ae21591649e75c82208f",
    "support"
   ],
   "docs/writing-tests/lint-tool.md": [
@@ -631283,12 +631293,12 @@
    "858758b4c8e022afe53d76184a65a44da8106a1b",
    "support"
   ],
-  "docs/writing-tests/testdriver-tutorial.md": [
-   "275c813355c6cb8e6b5e2e6c1595f40bde28e7ec",
+  "docs/writing-tests/testdriver-extension-tutorial.md": [
+   "262e394353632ccc4aaa8b42955d09a0de61624f",
    "support"
   ],
   "docs/writing-tests/testdriver.md": [
-   "99176906130c3812c9876fe72707175e35d961e8",
+   "6b398b993b61f835dc18b1a97019ab3d3d1377e0",
    "support"
   ],
   "docs/writing-tests/testharness-api.md": [
@@ -631300,7 +631310,7 @@
    "support"
   ],
   "docs/writing-tests/testharness.md": [
-   "17ee097ce185d07ac7353a1541c5c30593b9c387",
+   "acab70a1f1630cce6a270d8a966d166c90c23c22",
    "support"
   ],
   "docs/writing-tests/tools.md": [
@@ -661992,7 +662002,7 @@
    "support"
   ],
   "interfaces/html.idl": [
-   "8347c5d4cdc9b00550efcec7f2a77993f2b7ccf6",
+   "486875ec274f84ca5a6dae5c341b76119cc2e540",
    "support"
   ],
   "interfaces/image-capture.idl": [
diff --git a/tests/wpt/metadata/css/CSS2/linebox/inline-negative-margin-001.html.ini b/tests/wpt/metadata/css/CSS2/linebox/inline-negative-margin-001.html.ini
index 94a3570d26b..9f60026f6d9 100644
--- a/tests/wpt/metadata/css/CSS2/linebox/inline-negative-margin-001.html.ini
+++ b/tests/wpt/metadata/css/CSS2/linebox/inline-negative-margin-001.html.ini
@@ -5,9 +5,9 @@
   [[data-expected-height\] 7]
     expected: FAIL
 
-  [[data-expected-height\] 3]
+  [[data-expected-height\] 1]
     expected: FAIL
 
-  [[data-expected-height\] 4]
+  [[data-expected-height\] 2]
     expected: FAIL
 
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 ab300c199fb..8f3c2aded90 100644
--- a/tests/wpt/metadata/fetch/content-type/response.window.js.ini
+++ b/tests/wpt/metadata/fetch/content-type/response.window.js.ini
@@ -312,18 +312,21 @@
   [<iframe>: separate response Content-Type: */* text/html]
     expected: FAIL
 
-  [<iframe>: separate response Content-Type: text/plain */*;charset=gbk]
-    expected: FAIL
-
   [<iframe>: combined response Content-Type: text/html;" text/plain]
     expected: FAIL
 
-  [<iframe>: combined response Content-Type: text/html;x=" text/plain]
-    expected: FAIL
-
   [<iframe>: combined response Content-Type: */* text/html]
     expected: FAIL
 
-  [<iframe>: separate response Content-Type: text/html */*]
+  [<iframe>: combined response Content-Type: text/html */*]
+    expected: FAIL
+
+  [<iframe>: combined response Content-Type: text/html */*;charset=gbk]
+    expected: FAIL
+
+  [<iframe>: separate response Content-Type: text/html;x=" text/plain]
+    expected: FAIL
+
+  [<iframe>: combined response Content-Type: text/html;" \\" text/plain]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/fetch/content-type/script.window.js.ini b/tests/wpt/metadata/fetch/content-type/script.window.js.ini
index 258fe374697..c7413d589dc 100644
--- a/tests/wpt/metadata/fetch/content-type/script.window.js.ini
+++ b/tests/wpt/metadata/fetch/content-type/script.window.js.ini
@@ -56,6 +56,9 @@
   [separate text/javascript x/x]
     expected: FAIL
 
-  [separate text/javascript ]
+  [separate text/javascript;charset=windows-1252 error text/javascript]
+    expected: FAIL
+
+  [separate text/javascript;charset=windows-1252  text/javascript]
     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 87c807a49ff..a2a0c8f8200 100644
--- a/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini
+++ b/tests/wpt/metadata/fetch/nosniff/parsing-nosniff.window.js.ini
@@ -11,3 +11,9 @@
   [X-Content-Type-Options%3A%20nosniff%0C]
     expected: FAIL
 
+  [X-Content-Type-Options%3A%20'NosniFF']
+    expected: FAIL
+
+  [X-Content-Type-Options%3A%20%22nosniFF%22]
+    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_5.html.ini
deleted file mode 100644
index dc2e45516de..00000000000
--- a/tests/wpt/metadata/html/browsers/history/the-history-interface/traverse_the_history_5.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[traverse_the_history_5.html]
-  [Multiple history traversals, last would be aborted]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/html/browsers/origin/relaxing-the-same-origin-restriction/document_domain_access_details.sub.html.ini b/tests/wpt/metadata/html/browsers/origin/relaxing-the-same-origin-restriction/document_domain_access_details.sub.html.ini
index 8da94f60fc5..83d36d0a1ab 100644
--- a/tests/wpt/metadata/html/browsers/origin/relaxing-the-same-origin-restriction/document_domain_access_details.sub.html.ini
+++ b/tests/wpt/metadata/html/browsers/origin/relaxing-the-same-origin-restriction/document_domain_access_details.sub.html.ini
@@ -1,7 +1,7 @@
 [document_domain_access_details.sub.html]
   expected: TIMEOUT
   [Access allowed if same-origin with no 'document.domain' modification. (Sanity check)]
-    expected: TIMEOUT
+    expected: FAIL
 
   [Access is revoked to Window object when we stop being same effective script origin due to document.domain.]
     expected: NOTRUN
@@ -13,7 +13,7 @@
     expected: NOTRUN
 
   [Access not allowed if different-origin with no 'document.domain' modification. (Sanity check)]
-    expected: NOTRUN
+    expected: FAIL
 
   [Access disallowed again if same-origin, both set document-domain to existing value, then one sets to parent.]
     expected: NOTRUN
@@ -22,13 +22,13 @@
     expected: NOTRUN
 
   [Access allowed if same-origin and both set document.domain to existing value.]
-    expected: NOTRUN
+    expected: TIMEOUT
 
   [Access is not revoked to Document object when we stop being same effective script origin due to document.domain.]
     expected: NOTRUN
 
   [Access disallowed if same-origin but only one sets document.domain.]
-    expected: NOTRUN
+    expected: FAIL
 
   [Access evolves correctly for cross-origin objects when we join up via document.domain and then diverge again.]
     expected: NOTRUN
diff --git a/tests/wpt/metadata/html/browsers/windows/embedded-opener-remove-frame.html.ini b/tests/wpt/metadata/html/browsers/windows/embedded-opener-remove-frame.html.ini
index 2532dceabac..fd369192a02 100644
--- a/tests/wpt/metadata/html/browsers/windows/embedded-opener-remove-frame.html.ini
+++ b/tests/wpt/metadata/html/browsers/windows/embedded-opener-remove-frame.html.ini
@@ -1,5 +1,5 @@
 [embedded-opener-remove-frame.html]
-  expected: CRASH
+  expected: TIMEOUT
   [opener and "removed" embedded documents]
     expected: FAIL
 
@@ -7,5 +7,5 @@
     expected: FAIL
 
   [opener of discarded auxiliary browsing context]
-    expected: FAIL
+    expected: TIMEOUT
 
diff --git a/tests/wpt/metadata/html/dom/idlharness.https.html.ini b/tests/wpt/metadata/html/dom/idlharness.https.html.ini
index 1117320ad5e..5fe3f60866f 100644
--- a/tests/wpt/metadata/html/dom/idlharness.https.html.ini
+++ b/tests/wpt/metadata/html/dom/idlharness.https.html.ini
@@ -1391,6 +1391,27 @@
   [SVGAElement includes HTMLHyperlinkElementUtils: member names are unique]
     expected: FAIL
 
+  [SubmitEvent interface object name]
+    expected: FAIL
+
+  [SubmitEvent interface object length]
+    expected: FAIL
+
+  [SubmitEvent interface: existence and properties of interface prototype object]
+    expected: FAIL
+
+  [SubmitEvent interface: existence and properties of interface prototype object's @@unscopables property]
+    expected: FAIL
+
+  [SubmitEvent interface: attribute submitter]
+    expected: FAIL
+
+  [SubmitEvent interface: existence and properties of interface object]
+    expected: FAIL
+
+  [SubmitEvent interface: existence and properties of interface prototype object's "constructor" property]
+    expected: FAIL
+
 
 [idlharness.https.html?include=(Document|Window)]
   [Document interface: documentWithHandlers must inherit property "queryCommandEnabled(DOMString)" with the proper type]
diff --git a/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-3.html.ini b/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-3.html.ini
index f6a7aca3306..5f60c78e73c 100644
--- a/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-3.html.ini
+++ b/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-3.html.ini
@@ -1,5 +1,6 @@
 [iframe_sandbox_popups_escaping-3.html]
   type: testharness
+  expected: TIMEOUT
   [Check that popups from a sandboxed iframe escape the sandbox if\n       allow-popups-to-escape-sandbox is used]
-    expected: FAIL
+    expected: TIMEOUT
 
diff --git a/tests/wpt/metadata/html/semantics/forms/the-button-element/button-submit-children.html.ini b/tests/wpt/metadata/html/semantics/forms/the-button-element/button-submit-children.html.ini
new file mode 100644
index 00000000000..dbb4c200800
--- /dev/null
+++ b/tests/wpt/metadata/html/semantics/forms/the-button-element/button-submit-children.html.ini
@@ -0,0 +1,5 @@
+[button-submit-children.html]
+  expected: TIMEOUT
+  [This test will pass if a form navigation successfully occurs when clicking a child element of a <button type=submit> element with a onclick event handler which prevents the default form submission and manually calls form.submit() instead.]
+    expected: TIMEOUT
+
diff --git a/tests/wpt/metadata/html/semantics/interactive-elements/the-details-element/toggleEvent.html.ini b/tests/wpt/metadata/html/semantics/interactive-elements/the-details-element/toggleEvent.html.ini
deleted file mode 100644
index 9e522297c94..00000000000
--- a/tests/wpt/metadata/html/semantics/interactive-elements/the-details-element/toggleEvent.html.ini
+++ /dev/null
@@ -1,7 +0,0 @@
-[toggleEvent.html]
-  [Calling open twice on 'details' fires only one toggle event]
-    expected: FAIL
-
-  [Setting open=true to opened 'details' element should not fire a toggle event at the 'details' element]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/html/syntax/parsing/DOMContentLoaded-defer.html.ini b/tests/wpt/metadata/html/syntax/parsing/DOMContentLoaded-defer.html.ini
new file mode 100644
index 00000000000..a9677391662
--- /dev/null
+++ b/tests/wpt/metadata/html/syntax/parsing/DOMContentLoaded-defer.html.ini
@@ -0,0 +1,4 @@
+[DOMContentLoaded-defer.html]
+  [The end: DOMContentLoaded and defer scripts]
+    expected: FAIL
+
diff --git a/tests/wpt/metadata/offscreen-canvas/shadows/2d.shadow.offset.negativeX.html.ini b/tests/wpt/metadata/offscreen-canvas/shadows/2d.shadow.offset.negativeX.html.ini
index 7cab12e9647..c149ffb544c 100644
--- a/tests/wpt/metadata/offscreen-canvas/shadows/2d.shadow.offset.negativeX.html.ini
+++ b/tests/wpt/metadata/offscreen-canvas/shadows/2d.shadow.offset.negativeX.html.ini
@@ -1,4 +1,5 @@
 [2d.shadow.offset.negativeX.html]
+  expected: CRASH
   [Shadows can be offset with negative x]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/webaudio/the-audio-api/the-analysernode-interface/realtimeanalyser-fft-scaling.html.ini b/tests/wpt/metadata/webaudio/the-audio-api/the-analysernode-interface/realtimeanalyser-fft-scaling.html.ini
index 66bd350083b..a56bad443a2 100644
--- a/tests/wpt/metadata/webaudio/the-audio-api/the-analysernode-interface/realtimeanalyser-fft-scaling.html.ini
+++ b/tests/wpt/metadata/webaudio/the-audio-api/the-analysernode-interface/realtimeanalyser-fft-scaling.html.ini
@@ -1,4 +1,5 @@
 [realtimeanalyser-fft-scaling.html]
+  expected: TIMEOUT
   [X 2048-point FFT peak position is not equal to 64. Got 0.]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/webmessaging/with-ports/017.html.ini b/tests/wpt/metadata/webmessaging/with-ports/017.html.ini
new file mode 100644
index 00000000000..064cf47545b
--- /dev/null
+++ b/tests/wpt/metadata/webmessaging/with-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/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/metadata/workers/WorkerGlobalScope-close.html.ini b/tests/wpt/metadata/workers/WorkerGlobalScope-close.html.ini
deleted file mode 100644
index fe8654e447c..00000000000
--- a/tests/wpt/metadata/workers/WorkerGlobalScope-close.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[WorkerGlobalScope-close.html]
-  [Test sending a message after closing.]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/workers/baseurl/alpha/import-in-moduleworker.html.ini b/tests/wpt/metadata/workers/baseurl/alpha/import-in-moduleworker.html.ini
index bfd4d6dd2d6..bf2a1d61bab 100644
--- a/tests/wpt/metadata/workers/baseurl/alpha/import-in-moduleworker.html.ini
+++ b/tests/wpt/metadata/workers/baseurl/alpha/import-in-moduleworker.html.ini
@@ -1,5 +1,4 @@
 [import-in-moduleworker.html]
-  expected: ERROR
   [Base URL in module dedicated workers: import]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/workers/baseurl/alpha/sharedworker-in-worker.html.ini b/tests/wpt/metadata/workers/baseurl/alpha/sharedworker-in-worker.html.ini
index 650c91da4a6..333edb3a26e 100644
--- a/tests/wpt/metadata/workers/baseurl/alpha/sharedworker-in-worker.html.ini
+++ b/tests/wpt/metadata/workers/baseurl/alpha/sharedworker-in-worker.html.ini
@@ -1,5 +1,4 @@
 [sharedworker-in-worker.html]
-  expected: ERROR
   [Base URL in workers: new SharedWorker()]
     expected: FAIL
 
diff --git a/tests/wpt/metadata/workers/constructors/Worker/Worker-constructor.html.ini b/tests/wpt/metadata/workers/constructors/Worker/Worker-constructor.html.ini
deleted file mode 100644
index 80f9a4f15b8..00000000000
--- a/tests/wpt/metadata/workers/constructors/Worker/Worker-constructor.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[Worker-constructor.html]
-  expected: ERROR
diff --git a/tests/wpt/web-platform-tests/css/css-masking/animations/clip-path-interpolation.html b/tests/wpt/web-platform-tests/css/css-masking/animations/clip-path-interpolation-001.html
similarity index 100%
rename from tests/wpt/web-platform-tests/css/css-masking/animations/clip-path-interpolation.html
rename to tests/wpt/web-platform-tests/css/css-masking/animations/clip-path-interpolation-001.html
diff --git a/tests/wpt/web-platform-tests/css/css-masking/animations/clip-path-interpolation-002.html b/tests/wpt/web-platform-tests/css/css-masking/animations/clip-path-interpolation-002.html
new file mode 100644
index 00000000000..e00170ed331
--- /dev/null
+++ b/tests/wpt/web-platform-tests/css/css-masking/animations/clip-path-interpolation-002.html
@@ -0,0 +1,221 @@
+<!DOCTYPE html>
+<meta charset="UTF-8">
+<meta charset="UTF-8">
+<title>clip-path-interpolation</title>
+<link rel="help" href="https://drafts.fxtf.org/css-masking-1/#theclip-path">
+<meta name="assert" content="clip-path supports animation">
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/css/support/interpolation-testcommon.js"></script>
+
+<style>
+.parent {
+  clip-path: inset(10px);
+  padding: 10px;
+}
+
+.target {
+  display: inline-block;
+  width: 100px;
+  height: 100px;
+  background-color: black;
+  clip-path: inset(10px);
+}
+
+.expected {
+  background-color: green;
+}
+</style>
+<body>
+<script>
+test_interpolation({
+  property: 'clip-path',
+  from: neutralKeyframe,
+  to: 'inset(20px)',
+}, [
+  {at: -0.3, expect: 'inset(7px)'},
+  {at: 0, expect: 'inset(10px)'},
+  {at: 0.3, expect: 'inset(13px)'},
+  {at: 0.6, expect: 'inset(16px)'},
+  {at: 1, expect: 'inset(20px)'},
+  {at: 1.5, expect: 'inset(25px)'},
+]);
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'initial',
+  to: 'inset(20px)',
+});
+
+test_interpolation({
+  property: 'clip-path',
+  from: 'inherit',
+  to: 'inset(20px)',
+}, [
+  {at: -0.3, expect: 'inset(7px)'},
+  {at: 0, expect: 'inset(10px)'},
+  {at: 0.3, expect: 'inset(13px)'},
+  {at: 0.6, expect: 'inset(16px)'},
+  {at: 1, expect: 'inset(20px)'},
+  {at: 1.5, expect: 'inset(25px)'},
+]);
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'unset',
+  to: 'inset(20px)',
+});
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'none',
+  to: 'circle(3px at 1px 2px)',
+});
+
+test_interpolation({
+  property: 'clip-path',
+  from: 'circle(10px at 25px 75%)',
+  to: 'circle(50px at 50px center)'
+}, [
+  {at: -0.3, expect: 'circle(0px at 17.5px 82.5%)'}, // radius can't be negative
+  {at: 0, expect: 'circle(10px at 25px 75%)'},
+  {at: 0.3, expect: 'circle(22px at 32.5px 67.5%)'},
+  {at: 0.6, expect: 'circle(34px at 40px 60%)'},
+  {at: 1, expect: 'circle(50px at 50px 50%)'},
+  {at: 1.5, expect: 'circle(70px at 62.5px 37.5%)'},
+]);
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'circle(farthest-side at 25px 75%)',
+  to: 'circle(farthest-side at 50px center)'
+});
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'circle(closest-side at 10px 20px)',
+  to: 'circle(farthest-side at 30px 40px)',
+});
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'circle(50px at 10px 20px)',
+  to: 'circle(farthest-side at 30px 40px)',
+});
+
+test_interpolation({
+  property: 'clip-path',
+  from: 'ellipse(10px 20px at 25px 75px)',
+  to: 'ellipse(50px 100px at 50px 50px)',
+}, [
+  {at: -0.3, expect: 'ellipse(0px 0px at 17.5px 82.5px)'}, // radius can't be negative
+  {at: 0, expect: 'ellipse(10px 20px at 25px 75px)'},
+  {at: 0.3, expect: 'ellipse(22px 44px at 32.5px 67.5px)'},
+  {at: 0.6, expect: 'ellipse(34px 68px at 40px 60px)'},
+  {at: 1, expect: 'ellipse(50px 100px at 50px 50px)'},
+  {at: 1.5, expect: 'ellipse(70px 140px at 62.5px 37.5px)'},
+]);
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'ellipse(closest-side farthest-side at 25px 75%)',
+  to: 'ellipse(closest-side farthest-side at 50px center)',
+});
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'ellipse(closest-side farthest-side at 10px 20px)',
+  to: 'ellipse(farthest-side closest-side at 30px 40px)',
+});
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'ellipse(50px closest-side at 10px 20px)',
+  to: 'ellipse(150px farthest-side at 30px 40px)',
+});
+
+test_interpolation({
+  property: 'clip-path',
+  from: 'inset(20px)',
+  to: 'inset(40%)',
+}, [
+  {at: -0.3, expect: 'inset(calc(26px + -12%))'},
+  {at: 0, expect: 'inset(calc(20px + 0%))'},
+  {at: 0.3, expect: 'inset(calc(14px + 12%))'},
+  {at: 0.6, expect: 'inset(calc(8px + 24%))'},
+  {at: 1, expect: 'inset(40%)'},
+  {at: 1.5, expect: 'inset(calc(-10px + 60%))'},
+]);
+
+test_interpolation({
+  property: 'clip-path',
+  from: 'inset(1px 2px 3px 4px round 10px 20px 30px 40px / 50px 60px 70px 80px)',
+  to: 'inset(101px 102px 103px 104px round 110px 120px 130px 140px / 150px 160px 170px 180px)',
+}, [
+  {at: -0.3, expect: 'inset(-29px -28px -27px -26px round 0px 0px 0px 10px / 20px 30px 40px 50px)'},
+  {at: 0, expect: 'inset(1px 2px 3px 4px round 10px 20px 30px 40px / 50px 60px 70px 80px)'},
+  {at: 0.3, expect: 'inset(31px 32px 33px 34px round 40px 50px 60px 70px / 80px 90px 100px 110px)'},
+  {at: 0.6, expect: 'inset(61px 62px 63px 64px round 70px 80px 90px 100px / 110px 120px 130px 140px)'},
+  {at: 1, expect: 'inset(101px 102px 103px 104px round 110px 120px 130px 140px / 150px 160px 170px 180px)'},
+  {at: 1.5, expect: 'inset(151px 152px 153px 154px round 160px 170px 180px 190px / 200px 210px 220px 230px)'},
+]);
+
+test_interpolation({
+  property: 'clip-path',
+  from: 'inset(1px 2px round 100px 200px)',
+  to: 'inset(101px 102px 101px 102px)',
+}, [
+  {at: -0.3, expect: 'inset(-29px -28px round 130px 260px)'},
+  {at: 0, expect: 'inset(1px 2px round 100px 200px)'},
+  {at: 0.3, expect: 'inset(31px 32px round 70px 140px)'},
+  {at: 0.6, expect: 'inset(61px 62px round 40px 80px)'},
+  {at: 1, expect: 'inset(101px 102px)'},
+  {at: 1.5, expect: 'inset(151px 152px)'}, // border radius can't be negative
+]);
+
+test_interpolation({
+  property: 'clip-path',
+  from: 'polygon(10px 20%, 30px 40%)',
+  to: 'polygon(110px 120%, 130px 140%)',
+}, [
+  {at: -0.3, expect: 'polygon(-20px -10%, 0px 10%)'},
+  {at: 0, expect: 'polygon(10px 20%, 30px 40%)'},
+  {at: 0.3, expect: 'polygon(40px 50%, 60px 70%)'},
+  {at: 0.6, expect: 'polygon(70px 80%, 90px 100%)'},
+  {at: 1, expect: 'polygon(110px 120%, 130px 140%)'},
+  {at: 1.5, expect: 'polygon(160px 170%, 180px 190%)'},
+]);
+
+test_interpolation({
+  property: 'clip-path',
+  from: 'polygon(evenodd, 10px 20px)',
+  to: 'polygon(evenodd, 110px 120px)',
+}, [
+  {at: -0.3, expect: 'polygon(evenodd, -20px -10px)'},
+  {at: 0, expect: 'polygon(evenodd, 10px 20px)'},
+  {at: 0.3, expect: 'polygon(evenodd, 40px 50px)'},
+  {at: 0.6, expect: 'polygon(evenodd, 70px 80px)'},
+  {at: 1, expect: 'polygon(evenodd, 110px 120px)'},
+  {at: 1.5, expect: 'polygon(evenodd, 160px 170px)'},
+]);
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'polygon(evenodd, 10px 20px)',
+  to: 'polygon(nonzero, 110px 120px)',
+});
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'polygon(evenodd, 10px 20px)',
+  to: 'polygon(110px 120px)',
+});
+
+test_no_interpolation({
+  property: 'clip-path',
+  from: 'polygon(10px 20px, 30px 40px)',
+  to: 'polygon(110px 120px)',
+});
+</script>
+</body>
diff --git a/tests/wpt/web-platform-tests/docs/running-tests/from-local-system.md b/tests/wpt/web-platform-tests/docs/running-tests/from-local-system.md
index 0f337176c47..bc8b50ffd10 100644
--- a/tests/wpt/web-platform-tests/docs/running-tests/from-local-system.md
+++ b/tests/wpt/web-platform-tests/docs/running-tests/from-local-system.md
@@ -36,7 +36,7 @@ pip install --user virtualenv
 To make the `PATH` change persistent, add it to your `~/.bash_profile` file or
 wherever you currently set your PATH.
 
-See also [additional setup required to run Safari](safari).
+See also [additional setup required to run Safari](safari.md).
 
 ### Windows Setup
 **Note:** In general, Windows Subsystem for Linux will provide the smoothest
diff --git a/tests/wpt/web-platform-tests/docs/writing-tests/index.md b/tests/wpt/web-platform-tests/docs/writing-tests/index.md
index 0e0d3f35b00..84735b5ba36 100644
--- a/tests/wpt/web-platform-tests/docs/writing-tests/index.md
+++ b/tests/wpt/web-platform-tests/docs/writing-tests/index.md
@@ -28,7 +28,7 @@ There's also a load of [general guidelines](general-guidelines) that apply to al
    server-features
    submission-process
    testdriver
-   testdriver-tutorial
+   testdriver-extension-tutorial
    testharness
    testharness-tutorial
    tools
diff --git a/tests/wpt/web-platform-tests/docs/writing-tests/testdriver-tutorial.md b/tests/wpt/web-platform-tests/docs/writing-tests/testdriver-extension-tutorial.md
similarity index 99%
rename from tests/wpt/web-platform-tests/docs/writing-tests/testdriver-tutorial.md
rename to tests/wpt/web-platform-tests/docs/writing-tests/testdriver-extension-tutorial.md
index 275c813355c..262e3943536 100644
--- a/tests/wpt/web-platform-tests/docs/writing-tests/testdriver-tutorial.md
+++ b/tests/wpt/web-platform-tests/docs/writing-tests/testdriver-extension-tutorial.md
@@ -1,5 +1,4 @@
-# testdriver.js Tutorial
-
+# Testdriver extension tutorial
 Adding new commands to testdriver.js
 
 ## Assumptions
diff --git a/tests/wpt/web-platform-tests/docs/writing-tests/testdriver.md b/tests/wpt/web-platform-tests/docs/writing-tests/testdriver.md
index 99176906130..6b398b993b6 100644
--- a/tests/wpt/web-platform-tests/docs/writing-tests/testdriver.md
+++ b/tests/wpt/web-platform-tests/docs/writing-tests/testdriver.md
@@ -16,16 +16,22 @@ the global scope.
 NB: presently, testdriver.js only works in the top-level test browsing
 context (and not therefore in any frame or window opened from it).
 
-### action_sequence
-Usage: `test_driver.action_sequence(actions)`
- * `actions`: an array of `Action` objects
+### Actions
+Usage:
+```
+let actions = new test_driver.Actions()
+   .action1()
+   .action2();
+actions.send()
+```
 
-This function causes a sequence of actions to be sent to the browser. It is based on the [WebDriver API](https://w3c.github.io/webdriver/#actions).
+Test authors are encouraged to use the builder API to generate the sequence of actions. The builder
+API can be accessed via the `new test_driver.Actions()` object, and actions are defined in [testdriver-actions.js](https://github.com/web-platform-tests/wpt/blob/master/resources/testdriver-actions.js)
+
+The `actions.send()` function causes the sequence of actions to be sent to the browser. It is based on the [WebDriver API](https://w3c.github.io/webdriver/#actions).
 The action can be a keyboard action, a pointer action or a pause. It returns a `Promise` that
 resolves after the actions have been sent or rejects if an error was thrown.
 
-Test authors are encouraged to use the builder API to generate the sequence of actions. The builder
-API can be accessed via the `new test_driver.Actions()` object.
 
 Example:
 
diff --git a/tests/wpt/web-platform-tests/docs/writing-tests/testharness.md b/tests/wpt/web-platform-tests/docs/writing-tests/testharness.md
index 17ee097ce18..acab70a1f16 100644
--- a/tests/wpt/web-platform-tests/docs/writing-tests/testharness.md
+++ b/tests/wpt/web-platform-tests/docs/writing-tests/testharness.md
@@ -6,7 +6,7 @@
 
    idlharness
    testharness-api
-   testdriver-tutorial
+   testdriver-extension-tutorial
    testdriver
 ```
 
diff --git a/tests/wpt/web-platform-tests/interfaces/html.idl b/tests/wpt/web-platform-tests/interfaces/html.idl
index 8347c5d4cdc..486875ec274 100644
--- a/tests/wpt/web-platform-tests/interfaces/html.idl
+++ b/tests/wpt/web-platform-tests/interfaces/html.idl
@@ -266,9 +266,10 @@ interface HTMLQuoteElement : HTMLElement {
   [CEReactions] attribute USVString cite;
 };
 
-[Exposed=Window,
- HTMLConstructor]
+[Exposed=Window]
 interface HTMLOListElement : HTMLElement {
+  [HTMLConstructor] constructor();
+
   [CEReactions] attribute boolean reversed;
   [CEReactions] attribute long start;
   [CEReactions] attribute DOMString type;
@@ -283,16 +284,17 @@ interface HTMLUListElement : HTMLElement {
   // also has obsolete members
 };
 
-[Exposed=Window,
- HTMLConstructor]
+[Exposed=Window]
 interface HTMLMenuElement : HTMLElement {
+  [HTMLConstructor] constructor();
 
   // also has obsolete members
 };
 
-[Exposed=Window,
- HTMLConstructor]
+[Exposed=Window]
 interface HTMLLIElement : HTMLElement {
+  [HTMLConstructor] constructor();
+
   [CEReactions] attribute long value;
 
   // also has obsolete members
@@ -339,9 +341,10 @@ interface HTMLDataElement : HTMLElement {
   [CEReactions] attribute DOMString value;
 };
 
-[Exposed=Window,
- HTMLConstructor]
+[Exposed=Window]
 interface HTMLTimeElement : HTMLElement {
+  [HTMLConstructor] constructor();
+
   [CEReactions] attribute DOMString dateTime;
 };
 
@@ -396,9 +399,10 @@ interface HTMLSourceElement : HTMLElement {
 };
 
 [Exposed=Window,
- HTMLConstructor,
  NamedConstructor=Image(optional unsigned long width, optional unsigned long height)]
 interface HTMLImageElement : HTMLElement {
+  [HTMLConstructor] constructor();
+
   [CEReactions] attribute DOMString alt;
   [CEReactions] attribute USVString src;
   [CEReactions] attribute USVString srcset;
@@ -489,9 +493,10 @@ interface HTMLParamElement : HTMLElement {
   // also has obsolete members
 };
 
-[Exposed=Window,
- HTMLConstructor]
+[Exposed=Window]
 interface HTMLVideoElement : HTMLMediaElement {
+  [HTMLConstructor] constructor();
+
   [CEReactions] attribute unsigned long width;
   [CEReactions] attribute unsigned long height;
   readonly attribute unsigned long videoWidth;
@@ -501,9 +506,10 @@ interface HTMLVideoElement : HTMLMediaElement {
 };
 
 [Exposed=Window,
- HTMLConstructor,
  NamedConstructor=Audio(optional DOMString src)]
-interface HTMLAudioElement : HTMLMediaElement {};
+interface HTMLAudioElement : HTMLMediaElement {
+  [HTMLConstructor] constructor();
+};
 
 [Exposed=Window]
 interface HTMLTrackElement : HTMLElement {
@@ -818,9 +824,10 @@ interface HTMLTableCellElement : HTMLElement {
 
 [Exposed=Window,
  OverrideBuiltins,
- LegacyUnenumerableNamedProperties,
- HTMLConstructor]
+ LegacyUnenumerableNamedProperties]
 interface HTMLFormElement : HTMLElement {
+  [HTMLConstructor] constructor();
+
   [CEReactions] attribute DOMString acceptCharset;
   [CEReactions] attribute USVString action;
   [CEReactions] attribute DOMString autocomplete;
@@ -839,7 +846,7 @@ interface HTMLFormElement : HTMLElement {
   getter (RadioNodeList or Element) (DOMString name);
 
   void submit();
-  void requestSubmit(optional HTMLElement submitter);
+  void requestSubmit(optional HTMLElement? submitter = null);
   [CEReactions] void reset();
   boolean checkValidity();
   boolean reportValidity();
@@ -996,9 +1003,10 @@ interface HTMLOptGroupElement : HTMLElement {
 };
 
 [Exposed=Window,
- HTMLConstructor,
  NamedConstructor=Option(optional DOMString text = "", optional DOMString value, optional boolean defaultSelected = false, optional boolean selected = false)]
 interface HTMLOptionElement : HTMLElement {
+  [HTMLConstructor] constructor();
+
   [CEReactions] attribute boolean disabled;
   readonly attribute HTMLFormElement? form;
   [CEReactions] attribute DOMString label;
@@ -1147,6 +1155,17 @@ interface ValidityState {
   readonly attribute boolean valid;
 };
 
+[Exposed=Window]
+interface SubmitEvent : Event {
+  constructor(DOMString type, optional SubmitEventInit eventInitDict = {});
+
+  readonly attribute HTMLElement? submitter;
+};
+
+dictionary SubmitEventInit : EventInit {
+  HTMLElement? submitter = null;
+};
+
 [Exposed=Window,
  Constructor(DOMString type, optional FormDataEventInit eventInitDict = {})]
 interface FormDataEvent : Event {
@@ -1214,9 +1233,10 @@ dictionary AssignedNodesOptions {
 
 typedef (CanvasRenderingContext2D or ImageBitmapRenderingContext or WebGLRenderingContext or WebGL2RenderingContext) RenderingContext;
 
-[Exposed=Window,
- HTMLConstructor]
+[Exposed=Window]
 interface HTMLCanvasElement : HTMLElement {
+  [HTMLConstructor] constructor();
+
   [CEReactions] attribute unsigned long width;
   [CEReactions] attribute unsigned long height;