--- a/testing/web-platform/meta/content-security-policy/securitypolicyviolation/targeting.html.ini
+++ b/testing/web-platform/meta/content-security-policy/securitypolicyviolation/targeting.html.ini
@@ -1,18 +1,19 @@
 [targeting.html]
   type: testharness
+  prefs: [dom.webcomponents.enabled:true]
   expected: TIMEOUT
   [These tests should not fail.]
     expected: NOTRUN
 
   [Inline violations target the right element.]
     expected: TIMEOUT
 
   [Correct targeting inside shadow tree (inline handler).]
-    expected: FAIL
+    disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1404842#c19
 
   [Correct targeting inside shadow tree (style).]
-    expected: FAIL
+    disabled: https://bugzilla.mozilla.org/show_bug.cgi?id=1404842#c19
 
   [Elements created in this document, but pushed into a same-origin frame trigger on that frame's document, not on this frame's document.]
     expected: TIMEOUT
 

--- a/testing/web-platform/meta/cssom-view/elementsFromPoint-shadowroot.html.ini
+++ b/testing/web-platform/meta/cssom-view/elementsFromPoint-shadowroot.html.ini
@@ -1,5 +1,8 @@
 [elementsFromPoint-shadowroot.html]
   type: testharness
-  [Untitled]
+  prefs: [dom.webcomponents.enabled:true]
+  [elementsFromPoint on the document root should not return elements in shadow trees]
     expected: FAIL
 
+  [elementsFromPoint on a shadow root should include elements in that shadow tree]
+    expected: FAIL

new file mode 100644
--- /dev/null
+++ b/testing/web-platform/meta/cssom-view/scrollIntoView-shadow.html.ini
@@ -0,0 +1,3 @@
+[scrollIntoView-shadow.html]
+  type: testharness
+  prefs: [dom.webcomponents.enabled:true]

--- a/testing/web-platform/meta/custom-elements/adopted-callback.html.ini
+++ b/testing/web-platform/meta/custom-elements/adopted-callback.html.ini
@@ -1,86 +1,45 @@
 [adopted-callback.html]
   type: testharness
-  [Inserting a custom element into a shadow tree in the document of the template elements must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
+  prefs: [dom.webcomponents.enabled:true]
   [Inserting the shadow host of a custom element into the document of the template elements must enqueue and invoke adoptedCallback]
     expected: FAIL
 
   [Moving the shadow host of a custom element from the owner document into the document of the template elements must enqueue and invoke adoptedCallback]
     expected: FAIL
 
-  [Inserting a custom element into a detached shadow tree that belongs to the document of the template elements must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in a new document must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
   [Inserting the shadow host of a custom element into a new document must enqueue and invoke adoptedCallback]
     expected: FAIL
 
   [Moving the shadow host of a custom element from the owner document into a new document must enqueue and invoke adoptedCallback]
     expected: FAIL
 
-  [Inserting a custom element into a detached shadow tree that belongs to a new document must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in a cloned document must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
   [Inserting the shadow host of a custom element into a cloned document must enqueue and invoke adoptedCallback]
     expected: FAIL
 
   [Moving the shadow host of a custom element from the owner document into a cloned document must enqueue and invoke adoptedCallback]
     expected: FAIL
 
-  [Inserting a custom element into a detached shadow tree that belongs to a cloned document must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in a document created by createHTMLDocument must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
   [Inserting the shadow host of a custom element into a document created by createHTMLDocument must enqueue and invoke adoptedCallback]
     expected: FAIL
 
   [Moving the shadow host of a custom element from the owner document into a document created by createHTMLDocument must enqueue and invoke adoptedCallback]
     expected: FAIL
 
-  [Inserting a custom element into a detached shadow tree that belongs to a document created by createHTMLDocument must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in an HTML document created by createDocument must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
   [Inserting the shadow host of a custom element into an HTML document created by createDocument must enqueue and invoke adoptedCallback]
     expected: FAIL
 
   [Moving the shadow host of a custom element from the owner document into an HTML document created by createDocument must enqueue and invoke adoptedCallback]
     expected: FAIL
 
-  [Inserting a custom element into a detached shadow tree that belongs to an HTML document created by createDocument must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in the document of an iframe must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
   [Inserting the shadow host of a custom element into the document of an iframe must enqueue and invoke adoptedCallback]
     expected: FAIL
 
   [Moving the shadow host of a custom element from the owner document into the document of an iframe must enqueue and invoke adoptedCallback]
     expected: FAIL
 
-  [Inserting a custom element into a detached shadow tree that belongs to the document of an iframe must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in an HTML document fetched by XHR must enqueue and invoke adoptedCallback]
-    expected: FAIL
-
   [Inserting the shadow host of a custom element into an HTML document fetched by XHR must enqueue and invoke adoptedCallback]
     expected: FAIL
 
   [Moving the shadow host of a custom element from the owner document into an HTML document fetched by XHR must enqueue and invoke adoptedCallback]
     expected: FAIL
 
-  [Inserting a custom element into a detached shadow tree that belongs to an HTML document fetched by XHR must enqueue and invoke adoptedCallback]
-    expected: FAIL
-

--- a/testing/web-platform/meta/custom-elements/connected-callbacks.html.ini
+++ b/testing/web-platform/meta/custom-elements/connected-callbacks.html.ini
@@ -1,74 +1,3 @@
 [connected-callbacks.html]
   type: testharness
-  [Inserting a custom element into a shadow tree in the document must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting the shadow host of a custom element into the document must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a detached shadow tree that belongs to the document must not enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in the document of the template elements must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting the shadow host of a custom element into the document of the template elements must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a detached shadow tree that belongs to the document of the template elements must not enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in a new document must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting the shadow host of a custom element into a new document must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a detached shadow tree that belongs to a new document must not enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in a cloned document must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting the shadow host of a custom element into a cloned document must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a detached shadow tree that belongs to a cloned document must not enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in a document created by createHTMLDocument must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting the shadow host of a custom element into a document created by createHTMLDocument must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a detached shadow tree that belongs to a document created by createHTMLDocument must not enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in an HTML document created by createDocument must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting the shadow host of a custom element into an HTML document created by createDocument must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a detached shadow tree that belongs to an HTML document created by createDocument must not enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in the document of an iframe must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting the shadow host of a custom element into the document of an iframe must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a detached shadow tree that belongs to the document of an iframe must not enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a shadow tree in an HTML document fetched by XHR must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting the shadow host of a custom element into an HTML document fetched by XHR must enqueue and invoke connectedCallback]
-    expected: FAIL
-
-  [Inserting a custom element into a detached shadow tree that belongs to an HTML document fetched by XHR must not enqueue and invoke connectedCallback]
-    expected: FAIL
-
+  prefs: [dom.webcomponents.enabled:true]

--- a/testing/web-platform/meta/custom-elements/reactions/Element.html.ini
+++ b/testing/web-platform/meta/custom-elements/reactions/Element.html.ini
@@ -1,16 +1,11 @@
 [Element.html]
   type: testharness
-  [slot on Element must enqueue an attributeChanged reaction when adding slot content attribute]
-    expected: FAIL
-
-  [slot on Element must enqueue an attributeChanged reaction when replacing an existing attribute]
-    expected: FAIL
-
+  prefs: [dom.webcomponents.enabled:true]
   [removeAttribute on Element must not enqueue an attributeChanged reaction when removing an attribute that does not exist]
     expected: FAIL
 
   [removeAttributeNS on Element must not enqueue an attributeChanged reaction when removing an attribute that does not exist]
     expected: FAIL
 
   [removeAttributeNode on Element must not enqueue an attributeChanged reaction when removing an attribute that does not exist]
     expected: FAIL

--- a/testing/web-platform/meta/dom/interfaces.html.ini
+++ b/testing/web-platform/meta/dom/interfaces.html.ini
@@ -11,34 +11,16 @@
 
   [NodeFilter interface: existence and properties of interface object]
     bug: https://github.com/heycam/webidl/issues/96
 
   [Document interface: new Document() must inherit property "origin" with the proper type (3)]
     expected: FAIL
     bug: 931884
 
-  [ShadowRoot interface: attribute mode]
-    expected: FAIL
-
-  [Element interface: attribute slot]
-    expected: FAIL
-
-  [Element interface: operation attachShadow(ShadowRootInit)]
-    expected: FAIL
-
-  [Element interface: element must inherit property "slot" with the proper type (7)]
-    expected: FAIL
-
-  [Element interface: element must inherit property "attachShadow" with the proper type (24)]
-    expected: FAIL
-
-  [Element interface: calling attachShadow(ShadowRootInit) on element with too few arguments must throw TypeError]
-    expected: FAIL
-
   [Element interface: element must inherit property "assignedSlot" with the proper type (48)]
     expected: FAIL
 
   [Text interface: document.createTextNode("abc") must inherit property "assignedSlot" with the proper type (2)]
     expected: FAIL
 
   [EventTarget must be primary interface of new EventTarget()]
     expected: FAIL
@@ -85,15 +67,8 @@
   [AbortSignal interface: new AbortController().signal must inherit property "onabort" with the proper type]
     expected: FAIL
 
   [Document interface: new Document() must inherit property "origin" with the proper type]
     expected: FAIL
 
   [Document interface: xmlDoc must inherit property "origin" with the proper type]
     expected: FAIL
-
-  [Element interface: element must inherit property "slot" with the proper type]
-    expected: FAIL
-
-  [Element interface: element must inherit property "attachShadow(ShadowRootInit)" with the proper type]
-    expected: FAIL
-

--- a/testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/pragma-directives/attr-meta-http-equiv-refresh/not-in-shadow-tree.html.ini
+++ b/testing/web-platform/meta/html/semantics/document-metadata/the-meta-element/pragma-directives/attr-meta-http-equiv-refresh/not-in-shadow-tree.html.ini
@@ -1,5 +1,3 @@
 [not-in-shadow-tree.html]
   type: testharness
-  [Meta refresh only applies while in the document tree, not in a shadow tree]
-    expected: FAIL
-
+  prefs: [dom.webcomponents.enabled:true]

--- a/testing/web-platform/meta/html/semantics/forms/the-form-element/form-elements-filter.html.ini
+++ b/testing/web-platform/meta/html/semantics/forms/the-form-element/form-elements-filter.html.ini
@@ -1,5 +1,3 @@
 [form-elements-filter.html]
   type: testharness
-  [form.elements only includes elements from the same shadow tree]
-    expected: FAIL
-
+  prefs: [dom.webcomponents.enabled:true]

new file mode 100644
--- /dev/null
+++ b/testing/web-platform/meta/html/semantics/forms/the-label-element/label-attributes.html.ini
@@ -0,0 +1,3 @@
+[label-attributes.html]
+  type: testharness
+  prefs: [dom.webcomponents.enabled:true]

--- a/testing/web-platform/meta/payment-request/interfaces.https.html.ini
+++ b/testing/web-platform/meta/payment-request/interfaces.https.html.ini
@@ -263,25 +263,16 @@
     expected: FAIL
 
   [PaymentResponse interface: operation toJSON()]
     expected: FAIL
 
   [Document interface: attribute origin]
     expected: FAIL
 
-  [ShadowRoot interface: attribute mode]
-    expected: FAIL
-
-  [Element interface: attribute slot]
-    expected: FAIL
-
-  [Element interface: operation attachShadow(ShadowRootInit)]
-    expected: FAIL
-
   [PaymentRequest must be primary interface of new PaymentRequest([{supportedMethods: 'foo'}\], {total: {label: 'bar', amount: {currency: 'USD', value: '0'}} })]
     expected: FAIL
 
   [Stringification of new PaymentRequest([{supportedMethods: 'foo'}\], {total: {label: 'bar', amount: {currency: 'USD', value: '0'}} })]
     expected: FAIL
 
   [PaymentRequest interface: new PaymentRequest([{supportedMethods: 'foo'}\], {total: {label: 'bar', amount: {currency: 'USD', value: '0'}} }) must inherit property "show()" with the proper type]
     expected: FAIL

--- a/testing/web-platform/meta/touch-events/touch-retargeting.html.ini
+++ b/testing/web-platform/meta/touch-events/touch-retargeting.html.ini
@@ -1,5 +1,5 @@
 [touch-retargeting.html]
   type: testharness
-  [TouchEvent Retargeting Tests]
+  prefs: [dom.webcomponents.enabled:true]
+  [TouchEvent's touches, targetTouches, and changedTouches should be retargeted.]
     expected: FAIL
-