diff --git a/shadow-dom/reference-target/tentative/dom-mutation.html b/shadow-dom/reference-target/tentative/dom-mutation.html
index 12735bed701c58..91a94158ccf4da 100644
--- a/shadow-dom/reference-target/tentative/dom-mutation.html
+++ b/shadow-dom/reference-target/tentative/dom-mutation.html
@@ -33,7 +33,6 @@
   const test_container = await setup_test();
   const host1 = test_container.querySelector("#host1");
   const label1 = host1.shadowRoot.querySelector("#label1");
-
   label1.id = "new_id";
   assert_equals(await test_driver.get_computed_label(input1), "");
 }, "Changing the ID of the referenced element results in an empty computed label");
@@ -110,93 +109,7 @@
   real_label1.id = "new_id";
   assert_equals(await test_driver.get_computed_label(input1), "");
 }, "Changing the ID of the nested referenced element results in an empty computed label");
-</script>
-
-<label id="label2" for="x-input2">Input 2</label>
-<x-input2 id="x-input2">
-  <template shadowrootmode="open" shadowrootreferencetarget="input2">
-    <input id="input2">
-  </template>
-</x-input2>
-
-<script>
-promise_test(async t => {
-    const x_input = document.getElementById('x-input2');
-    const input = x_input.shadowRoot.getElementById('input2');
-    const label = document.getElementById('label2');
 
-    label.htmlFor = '';
-    assert_array_equals(Array.from(input['labels']), []);
-
-    label.htmlFor = x_input.id;
-    assert_array_equals(Array.from(input['labels']), [label]);
-}, ".labels property is updated when for attribute changes on label outside of shadow root");
 </script>
-
-<label id="label3" for="x-input3">Input 3</label>
-<x-input3 id="x-input3">
-  <template shadowrootmode="open" shadowrootreferencetarget="input3">
-    <input id="input3">
-  </template>
-</x-input3>
-
-<script>
-promise_test(async t => {
-    const x_input = document.getElementById('x-input3');
-    const input = x_input.shadowRoot.getElementById('input3');
-    const label = document.getElementById('label3');
-
-    x_input.removeAttribute('id');
-    assert_array_equals(Array.from(input['labels']), []);
-
-    x_input.id = label.htmlFor;
-    assert_array_equals(Array.from(input['labels']), [label]);
-}, ".labels property is updated when ID changes on input");
-</script>
-
-<label id="label4" for="x-input4">Input 4</label>
-<x-input4 id="x-input4">
-  <template shadowrootmode="open" shadowrootreferencetarget="input4">
-    <input id="input4">
-  </template>
-</x-input4>
-
-<script>
-promise_test(async t => {
-    const x_input = document.getElementById('x-input4');
-    const input = x_input.shadowRoot.getElementById('input4');
-    const label = document.getElementById('label4');
-
-    x_input.shadowRoot.referenceTarget = null;
-    assert_array_equals(Array.from(input['labels']), []);
-
-    x_input.shadowRoot.referenceTarget = input.id;
-    assert_array_equals(Array.from(input['labels']), [label]);
-}, ".labels property is updated when reference target changes on shadow root");
-</script>
-
-<label id="label5-A">A
-  <x-input5 id="x-input5">
-    <template shadowrootmode="open" shadowrootreferencetarget="input5">
-      <input id="input5">
-    </template>
-  </x-input5>
-</label>
-<label id="label5-B"></label>
-
-<script>
-promise_test(async t => {
-    const x_input = document.getElementById('x-input5');
-    const input = x_input.shadowRoot.getElementById('input5');
-    const A = document.getElementById('label5-A');
-
-    assert_array_equals(Array.from(input['labels']), [A]);
-
-    const B = document.getElementById('label5-B');
-    B.appendChild(x_input);
-    assert_array_equals(Array.from(input['labels']), [B]);
-}, ".labels property is updated when wrapped label changes");
-</script>
-
 </body>
 </html>
diff --git a/shadow-dom/reference-target/tentative/form.html b/shadow-dom/reference-target/tentative/form.html
index c2607f37fb6035..5ab144b05ed130 100644
--- a/shadow-dom/reference-target/tentative/form.html
+++ b/shadow-dom/reference-target/tentative/form.html
@@ -168,209 +168,5 @@
         assert_equals(realForm.elements[2], input, "The 3rd element should be the input inside the real form.");
       }, "Reference target works with nested shadow trees.");
   </script>
-
-
-  <button id="reset-button-6" type="reset" form="fancy-form-6"></button>
-
-
-  <script>
-    test(function() {
-      const resetButton = document.getElementById("reset-button-6");
-      assert_equals(resetButton.form, null, "The reset button doesn't have a form association before the form is created.");
-
-      // Construct disconnected custom element with shadow root
-      const fancyForm = document.createElement("fancy-form-6");
-      fancyForm.id = "fancy-form-6";
-      fancyForm.attachShadow({ mode: "open", referenceTarget: "real-form" });
-      const input = document.createElement("input");
-      input.id = "input-in-shadow";
-      input.setAttribute("value", "default value");
-      input.setAttribute("form", "real-form");
-      fancyForm.shadowRoot.appendChild(input);
-      assert_equals(input.form, null, "The inner input doesn't have a form association before the form is created.");
-
-      const realForm = document.createElement("form");
-      realForm.id = "real-form";
-      fancyForm.shadowRoot.appendChild(realForm);
-
-      assert_equals(realForm.elements.length, 0, "When the form is in disconnected DOM, it has no associated form elements.");
-      assert_equals(resetButton.form, null, "The reset button should not have a form before the form is connected to the document.");
-      assert_equals(input.form, null, "The inner input element should not have a form before the form is connected to the document.");
-
-      // Connect the custom element to the document
-      resetButton.after(fancyForm);
-
-      assert_equals(realForm.elements.length, 2, "Once the form is connected, it has two associated form elements.");
-      assert_equals(realForm.elements[0], resetButton, "The first element should be the reset button outside the shadow root.");
-      assert_equals(realForm.elements[1], input, "The second element should be the input element inside the shadow root.");
-      assert_equals(resetButton.form, fancyForm, "The reset button should show the shadow host as its form property.");
-      assert_equals(input.form, realForm, "The inner input element should show the actual form element as its form property.");
-      input.value = "new value";
-      assert_equals(input.value, "new value", "Before the reset button is clicked, the input element's value should be 'new value'.");
-      resetButton.click();
-      assert_equals(input.value, "default value", "After the reset button is clicked, the input element's value should be 'default value'.")
-
-      // Setting referenceTarget to null causes the reset button to no longer be
-      // associated with the form, but the inner input remains associated.
-      fancyForm.shadowRoot.referenceTarget = null;
-      assert_equals(realForm.elements.length, 1, "Once the reference target is set to null, the form should only have one form element.");
-      assert_equals(realForm.elements[0], input, "The sole element associated with the form should be the input element.");
-      assert_equals(resetButton.form, null, "The reset button should have null as its form property.");
-      assert_equals(input.form, realForm, "The inner input element should still have the form as its form property.");
-
-      input.value = "second new value";
-      assert_equals("second new value", input.value, "After the reference target is re-set, before the reset button is clicked, the input element's value should be 'new value'.");
-      resetButton.click();
-      assert_equals("second new value", input.value, "After the reference target is re-set, after the reset button is clicked, the input element's value should still be 'new new value'.")
-
-      realForm.remove();
-      assert_equals(realForm.elements.length, 0, "Before the inner-fancy-form containing the real form is inserted, it should have no associated form elements.");
-      assert_equals(input.form, null, "After the real form is removed from the first shadow root, the input should have no associated form");
-      assert_equals(resetButton.form, null, "After the real form is removed from the first shadow root, the reset button should have no associated form.");
-
-      // Adding a form nested inside another fancy-form with the appropriate
-      // referenceTarget values still causes the form association to be set up
-      const innerFancyForm = document.createElement('fancy-form-6');
-      innerFancyForm.id = "inner-fancy-form";
-      innerFancyForm.attachShadow({mode: "open", referenceTarget: "real-form"});
-      innerFancyForm.shadowRoot.appendChild(realForm);
-      fancyForm.shadowRoot.referenceTarget = "inner-fancy-form";
-      fancyForm.shadowRoot.appendChild(innerFancyForm);
-      assert_equals(realForm.elements.length, 1, "After the inner-fancy-form is connected, the real form should have 1 associated form elements");
-      assert_equals(realForm.elements[0], resetButton, "The associated element should be the reset button outside the shadow root.");
-      assert_equals(resetButton.form, fancyForm, "The reset button should have the outer fancy-form-6 as its form property.");
-      assert_equals(input.form, null, "The inner input element should have null as its form property.");
-
-      input.setAttribute("form", "inner-fancy-form");
-      assert_equals(realForm.elements.length, 2, "After the input's form attribute is updated, the real form should have 2 associated form elements");
-      assert_equals(realForm.elements[0], resetButton, "The first associated element should be the reset button outside the shadow root.");
-      assert_equals(realForm.elements[1], input, "The second associated element should be the input inside the first shadow root.");
-      assert_equals(resetButton.form, fancyForm, "The reset button should have the outer fancy-form-6 as its form property.");
-      assert_equals(input.form, innerFancyForm, "The inner input element should have the inner fancy-form-6 as its form property.");
-
-      input.value = "third new value";
-      assert_equals("third new value", input.value, "After the form is added to the nested shadow root, before the reset button is clicked, the input element's value should be 'new value'.");
-      resetButton.click();
-      assert_equals("default value", input.value, "After the form is added to the nested shadow root, after the reset button is clicked, the input element's value should still be 'new new value'.")
-
-      // Prepending an element with the same ID as the inner form causes all form associations to be reset to null
-      const fakeForm = document.createElement("div");
-      fakeForm.id = "real-form";
-      realForm.before(fakeForm);
-      assert_equals(realForm.elements.length, 0, "After an element with the same ID is inserted, the form should have no associated form elements.");
-      assert_equals(input.form, null, "After an element with the same ID as the form is inserted, the input should have no associated form");
-      assert_equals(resetButton.form, null, "After an element with the same ID as the form is inserted, the reset button should have no associated form.");
-
-      // Changing the ID of the inner form, and the reference target of the inner-fancy-form, causes the form associations to be recreated.
-      realForm.id = "real-form-redux";
-      innerFancyForm.shadowRoot.referenceTarget = "real-form-redux";
-      assert_equals(realForm.elements.length, 2, "After the ID of the inner form and reference target of inner-fancy-form are changed, the real form should have 2 associated form elements");
-      assert_equals(realForm.elements[0], resetButton, "After the ID of the inner form and reference target of inner-fancy-form are changed, the first associated element should be the reset button outside the shadow root.");
-      assert_equals(realForm.elements[1], input, "After the ID of the inner form and reference target of inner-fancy-form are changed, the second associated element should be the input inside the first shadow root.");
-      assert_equals(resetButton.form, fancyForm, "After the ID of the inner form and reference target of inner-fancy-form are changed, the reset button should have the outer fancy-form-6 as its form property.");
-      assert_equals(input.form, innerFancyForm, "After the ID of the inner form and reference target of inner-fancy-form are changed, the inner input element should have the inner fancy-form-6 as its form property.");
-
-      // Prepending an element with the same ID as the inner-fancy-form causes all form associations to be reset to null again
-      const fakeInnerFancyForm = document.createElement("div");
-      fakeInnerFancyForm.id = "inner-fancy-form"
-      innerFancyForm.before(fakeInnerFancyForm);
-
-      assert_equals(realForm.elements.length, 0, "After an element with the same ID as its shadow host is inserted, the form should have no associated form elements.");
-      assert_equals(input.form, null, "After an element with the same ID as the form's shadow host is inserted, the input should have no associated form");
-      assert_equals(resetButton.form, null, "After an element with the same ID as the form's shadow host is inserted, the reset button should have no associated form.");
-
-      // Removing that element should cause the form associations to be re-created
-      fakeInnerFancyForm.remove();
-      assert_equals(realForm.elements.length, 2, "After the fake inner-fancy-form is removed, the real form should have 2 associated form elements");
-      assert_equals(realForm.elements[0], resetButton, "After the fake inner-fancy-form is removed, the first associated element should be the reset button outside the shadow root.");
-      assert_equals(realForm.elements[1], input, "After the fake inner-fancy-form is removed, the second associated element should be the input inside the first shadow root.");
-      assert_equals(resetButton.form, fancyForm, "After the fake inner-fancy-form is removed, the reset button should have the outer fancy-form-6 as its form property.");
-      assert_equals(input.form, innerFancyForm, "After the fake inner-fancy-form is removed, the inner input element should have the inner fancy-form-6 as its form property.");
-
-      // Removing the ID of the real form causes all form associations to be reset to null
-      realForm.removeAttribute("id")
-      assert_equals(realForm.elements.length, 0, "After removing the ID of the real form, the form should have no associated form elements.");
-      assert_equals(input.form, null, "After removing the ID of the real form, the input should have no associated form");
-      assert_equals(resetButton.form, null, "After removing the ID of the real form, the reset button should have no associated form.");
-
-      // Reinstating the ID causes all associations to be re-created again
-      realForm.id = "real-form-redux";
-      assert_equals(realForm.elements.length, 2, "After the ID of the inner form is reinstated, the real form should have 2 associated form elements");
-      assert_equals(realForm.elements[0], resetButton, "After the ID of the inner form is reinstated, the first associated element should be the reset button outside the shadow root.");
-      assert_equals(realForm.elements[1], input, "After the ID of the inner form is reinstated, the second associated element should be the input inside the first shadow root.");
-      assert_equals(resetButton.form, fancyForm, "After the ID of the inner form is reinstated, the reset button should have the outer fancy-form-6 as its form property.");
-      assert_equals(input.form, innerFancyForm, "After the ID of the inner form is reinstated, the inner input element should have the inner fancy-form-6 as its form property.");
-
-      // Removing the inner form should cause the form-associated elements to have their forms set to null.
-      realForm.remove();
-      assert_equals(resetButton.form, null, "After removing the real form, the reset button should have the null form property.");
-      assert_equals(input.form, null, "After removing the real form, the inner input element should have null as its form property.");
-    }, "Form association is updated when form is inserted in or removed from shadow DOM, including in nested shadow DOM");
-  </script>
-
-  <input type="image" id="image-input-7" form="fancy-form-7">
-  <fancy-form-7 id="fancy-form-7">
-    <template shadowrootmode="open" shadowrootreferencetarget="real-form">
-      <form id="real-form">
-      </form>
-    </template>
-  </fancy-form-7>
-
-  <script>
-    test(function() {
-      let imageInput = document.getElementById("image-input-7");
-      let fancyForm = document.getElementById("fancy-form-7");
-      let realForm = fancyForm.shadowRoot.getElementById("real-form");
-
-      assert_equals(imageInput.form, fancyForm);
-      assert_equals(realForm.elements.length, 0);
-    }, "Form association works for image inputs, which aren't in the elements collection");
-  </script>
-
-
-  <input id="input-8" form="fancy-form-8" value="default value">
-  <fancy-form-8 id="fancy-form-8">
-    <template shadowRootMode="open">
-      <fancy-form-8 id="inner-fancy-form">
-        <template shadowRootMode="open">
-          <form id="real-form">
-            <button type="reset" id="reset">Reset</button>
-          </form>
-        </template>
-      </fancy-form-8>
-    </template>
-  </fancy-form-8>
-
-  <script>
-    test(function() {
-      let input = document.getElementById("input-8");
-      let outerFancyForm = document.getElementById("fancy-form-8");
-      let innerFancyForm = outerFancyForm.shadowRoot.getElementById("inner-fancy-form");
-      let realForm = innerFancyForm.shadowRoot.getElementById("real-form");
-      let resetButton = innerFancyForm.shadowRoot.getElementById("reset");
-
-      assert_equals(input.form, null, "Form is null before reference target change");
-      assert_equals(input.value, "default value", "Value is default");
-
-      input.value = "new value";
-      assert_equals(input.value, "new value", "Value is updated");
-
-      resetButton.click();
-      assert_equals(input.value, "new value", "Before reference target change, reset button doesn't reset outer input");
-
-      outerFancyForm.shadowRoot.referenceTarget = "inner-fancy-form";
-      assert_equals(input.form, null, "Form is still null after outer reference target change");
-      assert_equals(input.value, "new value", "Value is updated");
-
-      resetButton.click();
-      assert_equals(input.value, "new value", "After outer reference target change, reset button doesn't reset outer input");
-
-      innerFancyForm.shadowRoot.referenceTarget = "real-form";
-      assert_equals(input.form, outerFancyForm, "Form is outer-fancy-form after reference target change");
-
-      resetButton.click();
-      assert_equals(input.value, "default value", "After inner reference target change, reset resets outer input");
-    }, "Changing the reference target of a nested shadow root sets form association");
-  </script>
 </body>
 </html>
diff --git a/shadow-dom/reference-target/tentative/label-descendant.html b/shadow-dom/reference-target/tentative/label-descendant.html
index f3555077bb6fae..e6316175828b1c 100644
--- a/shadow-dom/reference-target/tentative/label-descendant.html
+++ b/shadow-dom/reference-target/tentative/label-descendant.html
@@ -2,7 +2,6 @@
 <html>
 
 <head>
-<script src="/html/resources/common.js"></script>
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <script src="/resources/testdriver.js"></script>
@@ -98,212 +97,6 @@
   testDeepImplicitLabelAssociation('x-outer2-a', 'Input 2 via Options');
 </script>
 
-
-<div id="test-container4"></div>
-<script>
-// The HTML5_LABELABLE_ELEMENTS are defined in https://html.spec.whatwg.org/#category-label
-for(let referenced_element_type of HTML5_LABELABLE_ELEMENTS) {
-  promise_test(async t => {
-    const test_container = document.querySelector("#test-container4");
-    test_container.setHTMLUnsafe(`
-      <label>
-      <fancy-element id="fancy">
-        <template shadowrootmode="open" shadowrootreferencetarget="target">
-          <${referenced_element_type} id="target"></${referenced_element_type}>
-        </template>
-      </fancy-element>
-      fancy custom element inside label
-      </label>`);
-
-    const fancy_element = document.getElementById('fancy');
-    const target_element = fancy_element.shadowRoot.getElementById('target');
-
-    assert_equals(await test_driver.get_computed_label(fancy_element), "");
-    assert_equals(await test_driver.get_computed_label(target_element), "fancy custom element inside label");
-  }, "Implicit <label> association should work with a custom element targeting '" + referenced_element_type + "' for computed name");
-
-  promise_test(async t => {
-    const test_container = document.querySelector("#test-container4");
-    test_container.setHTMLUnsafe(`
-      <label>
-      <fancy-element id="fancy">
-        <template shadowrootmode="open" shadowrootreferencetarget="target">
-          <${referenced_element_type} id="target"></${referenced_element_type}>
-        </template>
-      </fancy-element>
-      fancy custom element inside label
-      </label>`);
-
-    const fancy_element = document.getElementById('fancy');
-    const target_element = fancy_element.shadowRoot.getElementById('target');
-    const label = test_container.querySelector('label');
-
-    assert_array_equals(Array.from(target_element['labels']), [label]);
-  }, "Implicit <label> association should work with a custom element targeting '" + referenced_element_type + "' for .labels");
-}
-</script>
-
-
-<label id="label5">
-  <fancy-input id="fancy-input5-1">
-    <template shadowrootmode="open" shadowrootreferencetarget="real-input5-1">
-      <input id="real-input5-1">
-    </template>
-  </fancy-input>
-  <fancy-input id="fancy-input5-2">
-    <template shadowrootmode="open" shadowrootreferencetarget="real-input5-2">
-      <input id="real-input5-2">
-    </template>
-  </fancy-input>
-  fancy input inside label
-</label>
-<script>
-  promise_test(async t => {
-    const fancy_input1 = document.getElementById('fancy-input5-1');
-    const fancy_input2 = document.getElementById('fancy-input5-2');
-    const real_input1 = fancy_input1.shadowRoot.getElementById('real-input5-1');
-    const real_input2 = fancy_input2.shadowRoot.getElementById('real-input5-2');
-
-    assert_equals(await test_driver.get_computed_label(fancy_input1), "");
-    assert_equals(await test_driver.get_computed_label(fancy_input2), "");
-    assert_equals(await test_driver.get_computed_label(real_input1), "fancy input inside label");
-    assert_equals(await test_driver.get_computed_label(real_input2), "");
-
-    fancy_input2.after(fancy_input1);
-    assert_equals(await test_driver.get_computed_label(fancy_input1), "");
-    assert_equals(await test_driver.get_computed_label(fancy_input2), "");
-    assert_equals(await test_driver.get_computed_label(real_input1), "");
-    assert_equals(await test_driver.get_computed_label(real_input2), "fancy input inside label");
-  }, "Implicit <label> association should apply to only the first labelable custom element for computed name");
-</script>
-
-
-<label id="label6">
-  <fancy-input id="fancy-input6-1-outer">
-    <template shadowrootmode="open" >
-      <fancy-input id="fancy-input6-1-inner">
-        <template shadowrootmode="open">
-          <input id="real-input6-1">
-        </template>
-      </fancy-input>
-    </template>
-  </fancy-input>
-  <fancy-input id="fancy-input6-2">
-    <template shadowrootmode="open">
-      <input id="real-input6-2">
-    </template>
-  </fancy-input>
-  fancy input inside label
-</label>
-
-<script>
-  promise_test(async t => {
-    const fancy_input1_outer = document.getElementById('fancy-input6-1-outer');
-    fancy_input1_outer.shadowRoot.referenceTarget = 'fancy-input6-1-inner';
-    const fancy_input1_inner = fancy_input1_outer.shadowRoot.getElementById('fancy-input6-1-inner');
-    fancy_input1_inner.shadowRoot.referenceTarget = 'real-input6-1';
-    const fancy_input2 = document.getElementById('fancy-input6-2');
-    fancy_input2.shadowRoot.referenceTarget = 'real-input6-2';
-    const real_input1 = fancy_input1_inner.shadowRoot.getElementById('real-input6-1');
-    const real_input2 = fancy_input2.shadowRoot.getElementById('real-input6-2');
-    const label = document.getElementById('label6');
-
-    assert_array_equals(Array.from(real_input1['labels']), [label], "real_input1 initial");
-    assert_array_equals(Array.from(real_input2['labels']), [], "real_input2 initial");
-
-    fancy_input2.after(fancy_input1_outer);
-    assert_array_equals(Array.from(real_input1['labels']), [], "real_input1 after swap");
-    assert_array_equals(Array.from(real_input2['labels']), [label], "real_input2 after swap");
-
-    fancy_input2.shadowRoot.referenceTarget = null;
-    assert_array_equals(Array.from(real_input1['labels']), [label], "real_input1 after fancy_input2 referenceTarget change");
-    assert_array_equals(Array.from(real_input2['labels']), [], "real_input2 after fancy_input2 referenceTarget change");
-
-    fancy_input1_inner.shadowRoot.referenceTarget = null;
-    assert_array_equals(Array.from(real_input1['labels']), [], "real_input1 after fancy_input1_inner referenceTarget change");
-    assert_array_equals(Array.from(real_input2['labels']), [], "real_input2 after fancy_input1_inner referenceTarget change");
-
-    fancy_input1_inner.shadowRoot.referenceTarget = "real-input6-1";
-    assert_array_equals(Array.from(real_input1['labels']), [label], "real_input1 after second fancy_input1_inner referenceTarget change");
-    assert_array_equals(Array.from(real_input2['labels']), [], "real_input2 after second fancy_input1_inner referenceTarget change");
-  }, "Implicit <label> association should apply to only the first labelable custom element for .labels");
-</script>
-
-
-<label id="label-input7" for="fancy-input7-outer">Input 7
-  <fancy-input id="fancy-input7-outer">
-    <template shadowRootMode="open" shadowRootReferenceTarget="fancy-input7-inner">
-      <fancy-input id="fancy-input7-inner">
-        <template shadowrootmode="open" shadowrootreferencetarget="input7-1">
-          <input id="input7-1">
-          <input id="input7-2">
-        </template>
-      </fancy-input>
-    </template>
-  </fancy-input>
-</label>
-<script>
-  promise_test(async t => {
-    const outer_x_input = document.getElementById('fancy-input7-outer');
-    const outer_shadow = outer_x_input.shadowRoot;
-    const inner_x_input = outer_shadow.getElementById('fancy-input7-inner');
-    const inner_shadow = inner_x_input.shadowRoot;
-    const input1 = inner_shadow.getElementById('input7-1');
-    const input2 = inner_shadow.getElementById('input7-2');
-
-    assert_equals(await test_driver.get_computed_label(input1), "Input 7");
-    assert_equals(await test_driver.get_computed_label(input2), "");
-
-    inner_shadow.referenceTarget = "input7-2";
-
-    assert_equals(await test_driver.get_computed_label(input1), "");
-    assert_equals(await test_driver.get_computed_label(input2), "Input 7");
-
-    outer_shadow.referenceTarget = null;
-
-    assert_equals(await test_driver.get_computed_label(input1), "");
-    assert_equals(await test_driver.get_computed_label(input2), "");
-  }, "Changing the reference target causes label association to change for computed name");
-</script>
-
-<label id="label-input8" for="fancy-input8-outer">Input 8
-  <fancy-input id="fancy-input8-outer">
-    <template shadowRootMode="open" shadowRootReferenceTarget="fancy-input8-inner">
-      <fancy-input id="fancy-input8-inner">
-        <template shadowrootmode="open" shadowrootreferencetarget="input8-1">
-          <input id="input8-1">
-          <input id="input8-2">
-        </template>
-      </fancy-input>
-    </template>
-  </fancy-input>
-</label>
-<script>
-  promise_test(async t => {
-    const label = document.getElementById('label-input8');
-    const outer_x_input = document.getElementById('fancy-input8-outer');
-    const outer_shadow = outer_x_input.shadowRoot;
-    const inner_x_input = outer_shadow.getElementById('fancy-input8-inner');
-    const inner_shadow = inner_x_input.shadowRoot;
-    const input1 = inner_shadow.getElementById('input8-1');
-    const input2 = inner_shadow.getElementById('input8-2');
-
-    assert_array_equals(Array.from(input1['labels']), [label], 'input1 before change');
-    assert_array_equals(Array.from(input2['labels']), [], 'input2 before change');
-
-    inner_shadow.referenceTarget = "input8-2";
-
-    assert_array_equals(Array.from(input1['labels']), [], 'input1 after change');
-    assert_array_equals(Array.from(input2['labels']), [label], 'input2 after change');
-
-    outer_shadow.referenceTarget = null;
-
-    assert_array_equals(Array.from(input1['labels']), [], 'input1 after null');
-    assert_array_equals(Array.from(input2['labels']), [], 'input2 after null');
-  }, "Changing the reference target causes label association to change for .labels");
-
-</script>
-
 </body>
 
 </html>
diff --git a/shadow-dom/reference-target/tentative/label-for.html b/shadow-dom/reference-target/tentative/label-for.html
index 2d85b234edfbcf..05bb3511af4611 100644
--- a/shadow-dom/reference-target/tentative/label-for.html
+++ b/shadow-dom/reference-target/tentative/label-for.html
@@ -13,7 +13,7 @@
 
 <body>
 
-<label id="label1" for="x-input1">Input 1</label>
+<label for="x-input1">Input 1</label>
 <x-input1 id="x-input1">
   <template shadowrootmode="open" shadowrootreferencetarget="input1">
     <input id="input1">
@@ -27,18 +27,10 @@
     // The label should apply to the input element and not the host.
     assert_equals(await test_driver.get_computed_label(x_input), "");
     assert_equals(await test_driver.get_computed_label(input), "Input 1");
-  }, "Label for attribute targeting a custom element using shadowrootreferencetarget works for computed name");
-
-  promise_test(async t => {
-    const x_input = document.getElementById('x-input1');
-    const input = x_input.shadowRoot.getElementById('input1');
-    const label = document.getElementById('label1');
-
-    assert_array_equals(Array.from(input['labels']), [label]);
-}, "Label for attribute targeting a custom element using shadowrootreferencetarget works for .labels property");
+  }, "Label for attribute targets a custom element using shadowrootreferencetarget");
 </script>
 
-<label id="label2" for="x-outer2">Input 2</label>
+<label for="x-outer2">Input 2</label>
 <x-outer2 id="x-outer2">
   <template shadowrootmode="open" shadowrootreferencetarget="x-inner2">
     <x-inner2 id="x-inner2">
@@ -58,65 +50,40 @@
     assert_equals(await test_driver.get_computed_label(outer), "");
     assert_equals(await test_driver.get_computed_label(inner), "");
     assert_equals(await test_driver.get_computed_label(input), "Input 2");
-  }, "Label for attribute targeting a custom element using shadowrootreferencetarget inside multiple layers of shadow roots works for computed name");
-
-  promise_test(async t => {
-    const outer = document.getElementById('x-outer2');
-    const inner = outer.shadowRoot.getElementById('x-inner2');
-    const input = inner.shadowRoot.getElementById('input2');
-    const label = document.getElementById('label2');
-
-    assert_array_equals(Array.from(input['labels']), [label]);
-  }, "Label for attribute targeting a custom element using shadowrootreferencetarget inside multiple layers of shadow roots works for .labels property");
-
+  }, "Label for attribute targets a custom element using shadowrootreferencetarget inside multiple layers of shadow roots");
 </script>
 
-<label id="label3-A" for="x-outer3">A</label>
+<label for="x-outer3">A</label>
 <x-outer3 id="x-outer3">
   <template shadowrootmode="open" shadowrootreferencetarget="x-inner3">
-    <label id="label3-B" for="x-inner3">B</label>
+    <label for="x-inner3">B</label>
     <x-inner3 id="x-inner3">
       <template shadowrootmode="open" shadowrootreferencetarget="input3">
-        <label id="label3-C" for="input3">C</label>
+        <label for="input3">C</label>
         <input id="input3">
-        <label id="label3-D" for="input3">D</label>
+        <label for="input3">D</label>
       </template>
     </x-inner3>
-    <label id="label3-E" for="x-inner3">E</label>
+    <label for="x-inner3">E</label>
   </template>
 </x-outer3>
-<label id="label3-F" for="x-outer3">F</label>
+<label for="x-outer3">F</label>
 <script>
     promise_test(async t => {
       const outer = document.getElementById('x-outer3');
       const inner = outer.shadowRoot.getElementById('x-inner3');
       const input = inner.shadowRoot.getElementById('input3');
       const computed_label = await test_driver.get_computed_label(input);
-
       assert_equals(computed_label, "A B C D E F");
-    }, "Multiple labels targeting a custom element using shadowrootreferencetarget inside multiple layers of shadow roots works for computed name");
-
-    promise_test(async t => {
-      const outer = document.getElementById('x-outer3');
-      const inner = outer.shadowRoot.getElementById('x-inner3');
-      const input = inner.shadowRoot.getElementById('input3');
-      const A = document.getElementById('label3-A');
-      const B = outer.shadowRoot.getElementById('label3-B');
-      const C = inner.shadowRoot.getElementById('label3-C');
-      const D = inner.shadowRoot.getElementById('label3-D');
-      const E = outer.shadowRoot.getElementById('label3-E');
-      const F = document.getElementById('label3-F');
-
-      assert_array_equals(Array.from(input['labels']), [A, B, C, D, E, F]);
-    }, "Multiple labels targeting a custom element using shadowrootreferencetarget inside multiple layers of shadow roots works for .labels property");
+    }, "Multiple labels targeting a custom element using shadowrootreferencetarget inside multiple layers of shadow roots");
 </script>
 
 <label id="label-input4">Input 4</label>
-<x-input4 id="x-input4">
+<x-input1 id="x-input4">
   <template shadowrootmode="open" shadowrootreferencetarget="input4">
     <input id="input4">
   </template>
-</x-input4>
+</x-input1>
 <script>
   promise_test(async t => {
     const label = document.getElementById('label-input4');
@@ -127,200 +94,61 @@
     // The label should apply to the input element and not the host.
     assert_equals(await test_driver.get_computed_label(x_input), "");
     assert_equals(await test_driver.get_computed_label(input), "Input 4");
-  }, "Setting .htmlFor property to target a custom element using shadowrootreferencetarget works for computed name");
-
-  promise_test(async t => {
-    const label = document.getElementById('label-input4');
-    label.htmlFor = "x-input4";
-    const x_input = document.getElementById('x-input4');
-    const input = x_input.shadowRoot.getElementById('input4');
-
-    assert_array_equals(Array.from(input['labels']), [label]);
-  }, "Setting .htmlFor property to target a custom element using shadowrootreferencetarget works for .labels");
-
-</script>
-
-
-<label id="label-input5" for="x-input5-outer">Input 5</label>
-<x-input5 id="x-input5-outer">
-  <template shadowRootMode="open" shadowRootReferenceTarget="x-input5-inner">
-    <x-input5 id="x-input5-inner">
-      <template shadowrootmode="open" shadowrootreferencetarget="input5-1">
-        <input id="input5-1">
-        <input id="input5-2">
-      </template>
-    </x-input5>
-  </template>
-</x-input5>
-<script>
-  promise_test(async t => {
-    const outer_x_input = document.getElementById('x-input5-outer');
-    const outer_shadow_root = outer_x_input.shadowRoot;
-    const inner_x_input = outer_shadow_root.getElementById('x-input5-inner')
-    const inner_shadow_root = inner_x_input.shadowRoot;
-    const input1 = inner_shadow_root.getElementById('input5-1');
-    const input2 = inner_shadow_root.getElementById('input5-2');
-
-    assert_equals(await test_driver.get_computed_label(input1), "Input 5");
-    assert_equals(await test_driver.get_computed_label(input2), "");
-
-    inner_shadow_root.referenceTarget = 'input5-2';
-
-    assert_equals(await test_driver.get_computed_label(input1), "");
-    assert_equals(await test_driver.get_computed_label(input2), "Input 5");
-
-    outer_shadow_root.referenceTarget = null;
-
-    assert_equals(await test_driver.get_computed_label(input1), "");
-    assert_equals(await test_driver.get_computed_label(input2), "");
-  }, "Modifying the reference target changes the computed label when using label/for");
+  }, "Setting .htmlFor property to target a custom element using shadowrootreferencetarget");
 </script>
 
-<label id="label-input6" for="x-input6-outer">Input 6</label>
-<x-input6 id="x-input6-outer">
-  <template shadowRootMode="open" shadowRootReferenceTarget="x-input6-inner">
-    <x-input6 id="x-input6-inner">
-      <template shadowrootmode="open" shadowrootreferencetarget="input6-1">
-        <input id="input6-1">
-        <input id="input6-2">
-      </template>
-    </x-input6>
-  </template>
-</x-input6>
+<div id="test-container"></div>
 <script>
+// The HTML5_LABELABLE_ELEMENTS are defined in https://html.spec.whatwg.org/#category-label
+for(let referenced_element_type of HTML5_LABELABLE_ELEMENTS) {
   promise_test(async t => {
-    const label = document.getElementById('label-input6')
-    const outer_x_input = document.getElementById('x-input6-outer');
-    const outer_shadow_root = outer_x_input.shadowRoot;
-    const inner_x_input = outer_shadow_root.getElementById('x-input6-inner')
-    const inner_shadow_root = inner_x_input.shadowRoot;
-    const input1 = inner_shadow_root.getElementById('input6-1');
-    const input2 = inner_shadow_root.getElementById('input6-2');
-
-    assert_array_equals(Array.from(input1['labels']), [label], 'input1 before changing reference target');
-    assert_array_equals(Array.from(input2['labels']), [], 'input2 before changing reference target');
-
-    inner_shadow_root.referenceTarget = 'input6-2';
-
-    assert_array_equals(Array.from(input1['labels']), [], 'input1 after changing reference target');
-    assert_array_equals(Array.from(input2['labels']), [label], 'input2 after changing reference target');
-
-    outer_shadow_root.referenceTarget = null;
-
-    assert_array_equals(Array.from(input1['labels']), []);
-    assert_array_equals(Array.from(input2['labels']), []);
-  }, "Modifying the reference target changes .labels when using label/for");
-
+    const test_container = document.querySelector("#test-container");
+    test_container.setHTMLUnsafe(`
+      <label>
+      <fancy-element id="fancy">
+        <template shadowrootmode="open" shadowrootreferencetarget="target">
+          <${referenced_element_type} id="target"></${referenced_element_type}>
+        </template>
+      </fancy-element>
+      fancy custom element inside label
+      </label>`);
+
+    const fancy_element = document.getElementById('fancy');
+    const target_element = fancy_element.shadowRoot.getElementById('target');
+
+    assert_equals(await test_driver.get_computed_label(fancy_element), "");
+    assert_equals(await test_driver.get_computed_label(target_element), "fancy custom element inside label");
+  }, "Implicit <label> association should work with a custom element targeting '" + referenced_element_type + "'");
+}
 </script>
 
-<label id="label-input7-1" for="x-input7-1">Input 7 - 1</label>
-<x-input7 id="x-input7-1">
-  <template shadowRootMode="open" shadowRootReferenceTarget="input7">
-    <input id="input7">
+<label>
+<fancy-input id="fancy-input1">
+  <template shadowrootmode="open" shadowrootreferencetarget="real-input">
+    <input id="real-input">
   </template>
-</x-input7>
-
-<label id="label-input7-2" for="x-input7-2">Input 7 - 2</label>
-<x-input7 id="x-input7-2">
-  <template shadowRootMode="open" shadowRootReferenceTarget="input7">
+</fancy-input>
+<fancy-input id="fancy-input2">
+  <template shadowrootmode="open" shadowrootreferencetarget="real-input">
+    <input id="real-input">
   </template>
-</x-input7>
+</fancy-input>
+fancy input inside label
+</label>
 <script>
   promise_test(async t => {
-    const label_1 = document.getElementById('label-input7-1')
-    const x_input_1 = document.getElementById('x-input7-1');
-    const shadow_root_1 = x_input_1.shadowRoot;
-    const input = shadow_root_1.getElementById('input7');
-
-    assert_array_equals(Array.from(input['labels']), [label_1], 'input before changing shadow root');
-
-    const label_2 = document.getElementById('label-input7-2')
-    const x_input_2 = document.getElementById('x-input7-2');
-    const shadow_root_2 = x_input_2.shadowRoot;
-    shadow_root_2.append(input);
-
-    assert_array_equals(Array.from(input['labels']), [label_2], 'input after changing shadow root');
-  }, "Moving an input from one shadow root to another causes its .labels to be updated");
-
+    const fancy_input1 = document.getElementById('fancy-input1');
+    const fancy_input2 = document.getElementById('fancy-input2');
+    const real_input1 = fancy_input1.shadowRoot.getElementById('real-input');
+    const real_input2 = fancy_input2.shadowRoot.getElementById('real-input');
+
+    assert_equals(await test_driver.get_computed_label(fancy_input1), "");
+    assert_equals(await test_driver.get_computed_label(fancy_input2), "");
+    assert_equals(await test_driver.get_computed_label(real_input1), "fancy input inside label");
+    assert_equals(await test_driver.get_computed_label(real_input2), "");
+  }, "Implicit <label> association should apply to only the first labelable custom element");
 </script>
 
-
-<script>
-  promise_test(async t => {
-    const container = document.createElement('div');
-    container.id = 'container8';
-    const outer_label = document.createElement('label');
-    outer_label.id = 'outer-label8';
-    outer_label.htmlFor = 'outer-input8';
-    const light_input = document.createElement('input');
-    light_input.id = 'outer-input8'
-    assert_array_equals(Array.from(light_input.labels), [], 'before inserting light input');
-
-    container.append(outer_label, light_input);
-    assert_array_equals(Array.from(light_input.labels), [outer_label], 'after inserting light input in container');
-
-    document.body.append(container);
-    assert_array_equals(Array.from(light_input.labels), [outer_label], 'after inserting container in document');
-
-    light_input.remove();
-    assert_array_equals(Array.from(light_input.labels), [], 'after removing light input from document');
-
-    const inner_x_input = document.createElement('x-input8');
-    inner_x_input.id = 'inner-x-input8';
-    const inner_shadow_root = inner_x_input.attachShadow({mode: 'open'});
-    const inner_label = document.createElement('label');
-    inner_label.id = 'inner-label8';
-    inner_label.htmlFor = 'inner-input8';
-    inner_shadow_root.appendChild(inner_label);
-
-    const inner_input = document.createElement('input');
-    inner_input.id = 'inner-input8';
-    inner_shadow_root.appendChild(inner_input);
-
-    const outer_x_input = document.createElement('x-input8');
-    outer_x_input.id = 'outer-x-input8';
-    const outer_shadow_root = outer_x_input.attachShadow({mode: 'open'});
-    outer_shadow_root.referenceTarget = 'inner-x-input8';
-    const intermediate_label = document.createElement('label');
-    intermediate_label.id = 'intermediate-label8';
-    intermediate_label.htmlFor = 'inner-x-input8';
-    outer_shadow_root.appendChild(intermediate_label);
-    outer_shadow_root.appendChild(inner_x_input);
-
-    assert_array_equals(Array.from(inner_input['labels']), [inner_label], 'After inner shadow host is attached, before reference target is set');
-
-    inner_shadow_root.referenceTarget = 'inner-input8';
-    assert_array_equals(Array.from(inner_input['labels']), [intermediate_label, inner_label], 'After inner shadow reference target is set');
-
-    outer_label.htmlFor = 'outer-x-input8';
-    outer_label.after(outer_x_input);
-    assert_array_equals(Array.from(inner_input['labels']), [outer_label, intermediate_label, inner_label], 'After outer shadow host is inserted in the document');
-
-    outer_x_input.remove();
-    assert_array_equals(Array.from(inner_input['labels']), [intermediate_label, inner_label], 'After outer shadow host is removed from the document');
-
-    outer_label.after(outer_x_input);
-    assert_array_equals(Array.from(inner_input['labels']), [outer_label, intermediate_label, inner_label], 'After outer shadow host is re-inserted');
-
-    inner_x_input.remove();
-    assert_array_equals(Array.from(inner_input['labels']), [inner_label], 'After inner shadow host is removed from the document');
-
-    intermediate_label.after(inner_x_input);
-    assert_array_equals(Array.from(inner_input['labels']), [outer_label, intermediate_label, inner_label], 'After inner shadow host is re-inserted');
-
-    outer_shadow_root.referenceTarget = null;
-    assert_array_equals(Array.from(inner_input['labels']), [intermediate_label, inner_label], 'After outer shadow root reference target is set to null');
-
-    inner_shadow_root.referenceTarget = null;
-    assert_array_equals(Array.from(inner_input['labels']), [inner_label], 'After inner shadow root reference target is set to null');
-
-    inner_shadow_root.referenceTarget = 'inner-input8';
-    assert_array_equals(Array.from(inner_input['labels']), [intermediate_label, inner_label], 'After inner shadow root reference target is re-set');
-
-    outer_shadow_root.referenceTarget =  'inner-x-input8';
-    assert_array_equals(Array.from(inner_input['labels']), [outer_label, intermediate_label, inner_label], 'After outer shadow root reference target is re-set');
-  }, 'Attaching a shadow root, inserting and removing a shadow host, and changing reference targets all cause label association to be updated');
-
-</script>
 </body>
+
 </html>
diff --git a/tools/wptrunner/wptrunner/executors/actions.py b/tools/wptrunner/wptrunner/executors/actions.py
index e3177de19dd12f..785962062822bf 100644
--- a/tools/wptrunner/wptrunner/executors/actions.py
+++ b/tools/wptrunner/wptrunner/executors/actions.py
@@ -8,9 +8,9 @@ def __init__(self, logger, protocol):
         self.protocol = protocol
 
     def __call__(self, payload):
-        selectors = payload["selectors"]
-        element = self.protocol.select.element_by_selector_array(selectors)
-        self.logger.debug("Clicking element: %s" % selectors)
+        selector = payload["selector"]
+        element = self.protocol.select.element_by_selector(selector)
+        self.logger.debug("Clicking element: %s" % selector)
         self.protocol.click.element(element)
 
 
@@ -46,8 +46,8 @@ def __init__(self, logger, protocol):
         self.protocol = protocol
 
     def __call__(self, payload):
-        selectors = payload["selectors"]
-        element = self.protocol.select.element_by_selector_array(selectors)
+        selector = payload["selector"]
+        element = self.protocol.select.element_by_selector(selector)
         self.logger.debug("Getting computed label for element: %s" % element)
         return self.protocol.accessibility.get_computed_label(element)
 
@@ -60,8 +60,8 @@ def __init__(self, logger, protocol):
         self.protocol = protocol
 
     def __call__(self, payload):
-        selectors = payload["selectors"]
-        element = self.protocol.select.element_by_selector_array(selectors)
+        selector = payload["selector"]
+        element = self.protocol.select.element_by_selector(selector)
         self.logger.debug("Getting computed role for element: %s" % element)
         return self.protocol.accessibility.get_computed_role(element)
 
@@ -87,10 +87,10 @@ def __init__(self, logger, protocol):
         self.protocol = protocol
 
     def __call__(self, payload):
-        selectors = payload["selectors"]
+        selector = payload["selector"]
         keys = payload["keys"]
-        element = self.protocol.select.element_by_selector_array(selectors)
-        self.logger.debug("Sending keys to element: %s" % selectors)
+        element = self.protocol.select.element_by_selector(selector)
+        self.logger.debug("Sending keys to element: %s" % selector)
         self.protocol.send_keys.send_keys(element, keys)
 
 
@@ -145,11 +145,11 @@ def __call__(self, payload):
                 for action in actionSequence["actions"]:
                     if (action["type"] == "pointerMove" and
                         isinstance(action["origin"], dict)):
-                        action["origin"] = self.get_element(action["origin"]["selectors"])
+                        action["origin"] = self.get_element(action["origin"]["selector"])
         self.protocol.action_sequence.send_actions({"actions": actions})
 
-    def get_element(self, element_selectors):
-        return self.protocol.select.element_by_selector_array(element_selectors)
+    def get_element(self, element_selector):
+        return self.protocol.select.element_by_selector(element_selector)
 
     def reset(self):
         self.protocol.action_sequence.release()
diff --git a/tools/wptrunner/wptrunner/executors/executormarionette.py b/tools/wptrunner/wptrunner/executors/executormarionette.py
index ce9462f0523317..b3e3615c8bf6f9 100644
--- a/tools/wptrunner/wptrunner/executors/executormarionette.py
+++ b/tools/wptrunner/wptrunner/executors/executormarionette.py
@@ -403,26 +403,6 @@ class MarionetteSelectorProtocolPart(SelectorProtocolPart):
     def setup(self):
         self.marionette = self.parent.marionette
 
-    def elements_by_selector_array(self, selectors):
-        shadow_roots = []
-        selectors = selectors.copy()
-        selectors.reverse()
-
-        while selectors:
-            selector = selectors.pop()
-            intermediate = []
-            if not shadow_roots:
-                intermediate = self.marionette.find_elements("css selector", selector)
-            else:
-                for root in shadow_roots:
-                    intermediate.extend(root.find_elements("css selector", selector))
-
-            if (selectors):
-                shadow_roots = [element.shadow_root for element in intermediate]
-                shadow_roots = [root for root in shadow_roots if root is not None]
-            else:
-                return intermediate
-
     def elements_by_selector(self, selector):
         return self.marionette.find_elements("css selector", selector)
 
diff --git a/tools/wptrunner/wptrunner/executors/executorselenium.py b/tools/wptrunner/wptrunner/executors/executorselenium.py
index 0080367f6ed194..cf5ac2a22f02c5 100644
--- a/tools/wptrunner/wptrunner/executors/executorselenium.py
+++ b/tools/wptrunner/wptrunner/executors/executorselenium.py
@@ -171,12 +171,6 @@ class SeleniumSelectorProtocolPart(SelectorProtocolPart):
     def setup(self):
         self.webdriver = self.parent.webdriver
 
-    def elements_by_selector_array(self, selectors):
-        if len(selectors) == 1:
-            return self.elements_by_selector(selectors[0])
-
-        raise NotImplementedError()
-
     def elements_by_selector(self, selector):
         return self.webdriver.find_elements_by_css_selector(selector)
 
diff --git a/tools/wptrunner/wptrunner/executors/executorwebdriver.py b/tools/wptrunner/wptrunner/executors/executorwebdriver.py
index 2f59bfa1098624..cdb7deb5799747 100644
--- a/tools/wptrunner/wptrunner/executors/executorwebdriver.py
+++ b/tools/wptrunner/wptrunner/executors/executorwebdriver.py
@@ -531,12 +531,6 @@ class WebDriverSelectorProtocolPart(SelectorProtocolPart):
     def setup(self):
         self.webdriver = self.parent.webdriver
 
-    def elements_by_selector_array(self, selectors):
-        if len(selectors) == 1:
-            return self.elements_by_selector(selectors[0])
-
-        raise NotImplementedError()
-
     def elements_by_selector(self, selector):
         return self.webdriver.find.css(selector)
 
diff --git a/tools/wptrunner/wptrunner/executors/protocol.py b/tools/wptrunner/wptrunner/executors/protocol.py
index d5f215d4b9be05..d5f9b0bfc4bb89 100644
--- a/tools/wptrunner/wptrunner/executors/protocol.py
+++ b/tools/wptrunner/wptrunner/executors/protocol.py
@@ -285,24 +285,6 @@ class SelectorProtocolPart(ProtocolPart):
 
     name = "select"
 
-    def element_by_selector_array(self, element_selectors):
-        elements = self.elements_by_selector_array(element_selectors)
-        if len(elements) == 0:
-            raise ValueError(f"Selector array '{element_selectors}' matches no elements")
-        elif len(elements) > 1:
-            raise ValueError(f"Selector array '{element_selectors}' matches multiple elements")
-        return elements[0]
-
-    @abstractmethod
-    def elements_by_selector_array(self, selectors):
-        """Select elements matching an array of selectors, such that the first
-        selector matches an element in the document root, and each successive
-        selector matches an element inside the shadow root of the previous.
-
-        :param List[str] selectors: The CSS selectors
-        :returns: A list of protocol-specific handles to elements"""
-        pass
-
     def element_by_selector(self, element_selector):
         elements = self.elements_by_selector(element_selector)
         if len(elements) == 0:
diff --git a/tools/wptrunner/wptrunner/testdriver-extra.js b/tools/wptrunner/wptrunner/testdriver-extra.js
index f8b83097c58a71..6f6b13620782f5 100644
--- a/tools/wptrunner/wptrunner/testdriver-extra.js
+++ b/tools/wptrunner/wptrunner/testdriver-extra.js
@@ -78,7 +78,7 @@
         } else {
             if (bits >= 1 && bits <= 30) {
                 return 0 | ((1 << bits) * Math.random());
-             } else {
+            } else {
                 var high = (0 | ((1 << (bits - 30)) * Math.random())) * (1 << 30);
                 var low = 0 | ((1 << 30) * Math.random());
                 return  high + low;
@@ -134,18 +134,14 @@
         } else {
             // push and then reverse to avoid O(n) unshift in the loop
             let segments = [];
-            let el = element;
-            while (el && el.parentElement) {
-                let segment = "*|" + el.localName;
-                let nth = Array.prototype.indexOf.call(el.parentNode.children, el) + 1;
+            for (let node = element;
+                 node.parentElement;
+                 node = node.parentElement) {
+                let segment = "*|" + node.localName;
+                let nth = Array.prototype.indexOf.call(node.parentElement.children, node) + 1;
                 segments.push(segment + ":nth-child(" + nth + ")");
-                el = el.parentElement;
-            }
-            if (element.getRootNode() == element.ownerDocument) {
-              segments.push(":root");
-            } else {
-              segments.push(":scope");
             }
+            segments.push(":root");
             segments.reverse();
 
             selector = segments.join(" > ");
@@ -154,18 +150,6 @@
         return selector;
     };
 
-    const get_selector_array = function(element) {
-        let selectors = [];
-        let current = element;
-
-        do {
-            selectors.push(get_selector(current));
-            current = current.getRootNode().host;
-        } while (current);
-
-        return selectors.reverse();
-    };
-
     /**
      * Create an action and return a promise that resolves when the action is complete.
      * @param name: The name of the action to create.
@@ -476,9 +460,9 @@
     };
 
     window.test_driver_internal.click = function(element) {
-        const selectors = get_selector_array(element);
+        const selector = get_selector(element);
         const context = get_context(element);
-        return create_context_action("click", context, {selectors});
+        return create_context_action("click", context, {selector});
     };
 
     window.test_driver_internal.delete_all_cookies = function(context=null) {
@@ -498,15 +482,15 @@
     }
 
     window.test_driver_internal.get_computed_label = function(element) {
-        const selectors = get_selector_array(element);
+        const selector = get_selector(element);
         const context = get_context(element);
-        return create_context_action("get_computed_label", context, {selectors});
+        return create_context_action("get_computed_label", context, {selector});
     };
 
     window.test_driver_internal.get_computed_role = function(element) {
-        const selectors = get_selector_array(element);
+        const selector = get_selector(element);
         const context = get_context(element);
-        return create_context_action("get_computed_role", context, {selectors});
+        return create_context_action("get_computed_role", context, {selector});
     };
 
     window.test_driver_internal.get_named_cookie = function(name, context=null) {
@@ -526,9 +510,9 @@
     };
 
     window.test_driver_internal.send_keys = function(element, keys) {
-        const selectors = get_selector_array(element);
+        const selector = get_selector(element);
         const context = get_context(element);
-        return create_context_action("send_keys", context, {selectors, keys});
+        return create_context_action("send_keys", context, {selector, keys});
     };
 
     window.test_driver_internal.action_sequence = function(actions, context=null) {
@@ -538,7 +522,7 @@
                     // The origin of each action can only be an element or a string of a value "viewport" or "pointer".
                     if (action.type == "pointerMove" && typeof(action.origin) != 'string') {
                         let action_context = get_context(action.origin);
-                        action.origin = {selectors: get_selector_array(action.origin)};
+                        action.origin = {selector: get_selector(action.origin)};
                         if (context !== null && action_context !== context) {
                             throw new Error("Actions must be in a single context");
                         }