--- a/dom/html/test/mochitest.ini
+++ b/dom/html/test/mochitest.ini
@@ -435,17 +435,17 @@ support-files =
 [test_formData.html]
 [test_formSubmission.html]
 skip-if = toolkit == 'android' #TIMED_OUT
 [test_formSubmission2.html]
 skip-if = toolkit == 'android'
 [test_formelements.html]
 [test_fullscreen-api.html]
 tags = fullscreen
-skip-if = toolkit == 'android' || !stylo
+skip-if = toolkit == 'android'
 support-files =
   file_fullscreen-api.html
   file_fullscreen-backdrop.html
   file_fullscreen-denied-inner.html
   file_fullscreen-denied.html
   file_fullscreen-esc-exit-inner.html
   file_fullscreen-esc-exit.html
   file_fullscreen-hidden.html

--- a/dom/html/test/test_fullscreen-api.html
+++ b/dom/html/test/test_fullscreen-api.html
@@ -69,16 +69,23 @@ var gLinuxE10sSkipList = [
 ];
 
 function shouldSkipTest(test) {
   if (SpecialPowers.Cc["@mozilla.org/gfx/info;1"].getService(SpecialPowers.Ci.nsIGfxInfo).isHeadless &&
       test == "file_fullscreen-plugins.html") {
     todo(false, `${test} skipped due to bug 1409805`);
     return true;
   }
+
+  if (!SpecialPowers.DOMWindowUtils.isStyledByServo &&
+      test == "file_fullscreen-shadowdom.html") {
+    // Shadow DOM is stylo-only.
+    return true;
+  }
+
   if (!SpecialPowers.isMainProcess() &&
       navigator.platform.includes('Linux')) {
     for (let item of gLinuxE10sSkipList) {
       if (item.test == test) {
         todo(false, `${test} skipped due to ${item.reason}`);
         return true;
       }
     }

--- a/layout/reftests/webcomponents/reftest.list
+++ b/layout/reftests/webcomponents/reftest.list
@@ -1,23 +1,23 @@
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == cross-tree-selection-1.html cross-tree-selection-1-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-shadow-1.html basic-shadow-1-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-shadow-2.html basic-shadow-2-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-shadow-3.html basic-shadow-3-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-shadow-4.html basic-shadow-4-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == fallback-content-1.html fallback-content-1-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == remove-insertion-point-1.html remove-insertion-point-1-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == nested-insertion-point-1.html nested-insertion-point-1-ref.html
-pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == update-dist-node-descendants-1.html update-dist-node-descendants-1-ref.html
-pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) fuzzy-if(Android,2,7) == input-transition-1.html input-transition-1-ref.html
-pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == dynamic-insertion-point-distribution-1.html dynamic-insertion-point-distribution-1-ref.html
-pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == dynamic-insertion-point-distribution-2.html dynamic-insertion-point-distribution-2-ref.html
+pref(dom.webcomponents.shadowdom.enabled,true) skip-if(!stylo||styloVsGecko) == update-dist-node-descendants-1.html update-dist-node-descendants-1-ref.html
+pref(dom.webcomponents.shadowdom.enabled,true) skip-if(!stylo||styloVsGecko) fuzzy-if(Android,2,7) == input-transition-1.html input-transition-1-ref.html
+pref(dom.webcomponents.shadowdom.enabled,true) skip-if(!stylo||styloVsGecko) == dynamic-insertion-point-distribution-1.html dynamic-insertion-point-distribution-1-ref.html
+pref(dom.webcomponents.shadowdom.enabled,true) skip-if(!stylo||styloVsGecko) == dynamic-insertion-point-distribution-2.html dynamic-insertion-point-distribution-2-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == remove-append-shadow-host-1.html remove-append-shadow-host-1-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == reframe-shadow-child-1.html reframe-shadow-child-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == reframe-shadow-child-2.html reframe-shadow-child-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == style-sharing.html style-sharing-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) skip-if(!stylo||styloVsGecko) == style-sharing-across-shadow.html style-sharing-ref.html # bug 1412400
-pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-slot-1.html basic-slot-1-ref.html
-pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-slot-2.html basic-slot-2-ref.html
+pref(dom.webcomponents.shadowdom.enabled,true) == basic-slot-1.html basic-slot-1-ref.html
+pref(dom.webcomponents.shadowdom.enabled,true) == basic-slot-2.html basic-slot-2-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-slot-3.html basic-slot-3-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-slot-4.html basic-slot-3-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-slot-5.html basic-slot-5-ref.html
 pref(dom.webcomponents.shadowdom.enabled,true) fails-if(!stylo||styloVsGecko) == basic-slot-6.html basic-slot-6-ref.html

--- a/testing/web-platform/meta/css/cssom-view/elementsFromPoint-shadowroot.html.ini
+++ b/testing/web-platform/meta/css/cssom-view/elementsFromPoint-shadowroot.html.ini
@@ -1,2 +1,4 @@
 [elementsFromPoint-shadowroot.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo only.

--- a/testing/web-platform/meta/css/cssom-view/scrollIntoView-shadow.html.ini
+++ b/testing/web-platform/meta/css/cssom-view/scrollIntoView-shadow.html.ini
@@ -1,2 +1,4 @@
 [scrollIntoView-shadow.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo only.

--- a/testing/web-platform/meta/css/selectors/focus-within-shadow-002.html.ini
+++ b/testing/web-platform/meta/css/selectors/focus-within-shadow-002.html.ini
@@ -1,3 +1,3 @@
-[focus-within-shadow-001.html]
+[focus-within-shadow-002.html]
   disabled:
     if not stylo: Shadow DOM is stylo-only

--- a/testing/web-platform/meta/css/selectors/focus-within-shadow-003.html.ini
+++ b/testing/web-platform/meta/css/selectors/focus-within-shadow-003.html.ini
@@ -1,3 +1,3 @@
-[focus-within-shadow-001.html]
+[focus-within-shadow-003.html]
   disabled:
     if not stylo: Shadow DOM is stylo-only

--- a/testing/web-platform/meta/css/selectors/focus-within-shadow-004.html.ini
+++ b/testing/web-platform/meta/css/selectors/focus-within-shadow-004.html.ini
@@ -1,3 +1,3 @@
-[focus-within-shadow-001.html]
+[focus-within-shadow-004.html]
   disabled:
     if not stylo: Shadow DOM is stylo-only

--- a/testing/web-platform/meta/css/selectors/focus-within-shadow-005.html.ini
+++ b/testing/web-platform/meta/css/selectors/focus-within-shadow-005.html.ini
@@ -1,3 +1,3 @@
-[focus-within-shadow-001.html]
+[focus-within-shadow-005.html]
   disabled:
     if not stylo: Shadow DOM is stylo-only

--- a/testing/web-platform/meta/css/selectors/focus-within-shadow-006.html.ini
+++ b/testing/web-platform/meta/css/selectors/focus-within-shadow-006.html.ini
@@ -1,3 +1,3 @@
-[focus-within-shadow-001.html]
+[focus-within-shadow-006.html]
   disabled:
     if not stylo: Shadow DOM is stylo-only

--- a/testing/web-platform/meta/custom-elements/adopted-callback.html.ini
+++ b/testing/web-platform/meta/custom-elements/adopted-callback.html.ini
@@ -1,2 +1,4 @@
 [adopted-callback.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo-only.

--- a/testing/web-platform/meta/custom-elements/connected-callbacks.html.ini
+++ b/testing/web-platform/meta/custom-elements/connected-callbacks.html.ini
@@ -1,2 +1,4 @@
 [connected-callbacks.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo-only.

--- a/testing/web-platform/meta/custom-elements/disconnected-callbacks.html.ini
+++ b/testing/web-platform/meta/custom-elements/disconnected-callbacks.html.ini
@@ -1,2 +1,4 @@
 [disconnected-callbacks.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo-only.

--- a/testing/web-platform/meta/custom-elements/reactions/Element.html.ini
+++ b/testing/web-platform/meta/custom-elements/reactions/Element.html.ini
@@ -1,10 +1,13 @@
 [Element.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo only.
+
   [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/custom-elements/reactions/ShadowRoot.html.ini
+++ b/testing/web-platform/meta/custom-elements/reactions/ShadowRoot.html.ini
@@ -1,2 +1,4 @@
 [ShadowRoot.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo-only.

--- a/testing/web-platform/meta/dom/interfaces.html.ini
+++ b/testing/web-platform/meta/dom/interfaces.html.ini
@@ -1,10 +1,12 @@
 [interfaces.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo-only.
   [Document interface: attribute origin]
     expected: FAIL
     bug: 931884
 
   [Document interface: xmlDoc must inherit property "origin" with the proper type (3)]
     expected: FAIL
     bug: 931884
 

--- a/testing/web-platform/meta/html/dom/interfaces.html.ini
+++ b/testing/web-platform/meta/html/dom/interfaces.html.ini
@@ -1,10 +1,12 @@
 [interfaces.html]
   prefs: [dom.forms.inputmode:true, dom.dialog_element.enabled:true, dom.forms.autocomplete.formautofill:true, dom.webcomponents.shadowdom.enabled:true, browser.cache.offline.insecure.enable:true, dom.registerProtocolHandler.insecure.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo-only.
   [Document interface: attribute domain]
     expected: FAIL
 
   [Document interface: attribute cookie]
     expected: FAIL
 
   [Document interface: attribute head]
     expected: FAIL

--- a/testing/web-platform/meta/html/dom/reflection-misc.html.ini
+++ b/testing/web-platform/meta/html/dom/reflection-misc.html.ini
@@ -1,10 +1,12 @@
 [reflection-misc.html]
   prefs: [dom.dialog_element.enabled: true, dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo only.
   [html.tabIndex: setAttribute() to object "3" followed by getAttribute()]
     expected: FAIL
 
   [html.tabIndex: setAttribute() to object "3" followed by IDL get]
     expected: FAIL
 
   [script.tabIndex: setAttribute() to object "3" followed by getAttribute()]
     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
@@ -1,2 +1,4 @@
 [not-in-shadow-tree.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo only.

--- 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
@@ -1,2 +1,4 @@
 [form-elements-filter.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo-only.

--- a/testing/web-platform/meta/html/semantics/forms/the-label-element/label-attributes.html.ini
+++ b/testing/web-platform/meta/html/semantics/forms/the-label-element/label-attributes.html.ini
@@ -1,2 +1,4 @@
 [label-attributes.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo only.

--- a/testing/web-platform/meta/html/semantics/interfaces.html.ini
+++ b/testing/web-platform/meta/html/semantics/interfaces.html.ini
@@ -1,22 +1,30 @@
 [interfaces.html]
   prefs: [dom.dialog_element.enabled: true, dom.webcomponents.shadowdom.enabled:true]
+  [Interfaces for slot]
+    expected:
+      if not stylo: FAIL
+
   [Interfaces for image]
     expected: FAIL
 
   [Interfaces for keygen]
     expected: FAIL
 
   [Interfaces for marquee]
     expected: FAIL
 
   [Interfaces for bdi]
     expected: FAIL
 
+  [Interfaces for SLOT]
+    expected:
+      if not stylo: FAIL
+
   [Interfaces for IMAGE]
     expected: FAIL
 
   [Interfaces for KEYGEN]
     expected: FAIL
 
   [Interfaces for MARQUEE]
     expected: FAIL

--- a/testing/web-platform/meta/intersection-observer/shadow-content.html.ini
+++ b/testing/web-platform/meta/intersection-observer/shadow-content.html.ini
@@ -1,2 +1,4 @@
 [shadow-content.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo-only.

--- a/testing/web-platform/meta/payment-request/interfaces.https.html.ini
+++ b/testing/web-platform/meta/payment-request/interfaces.https.html.ini
@@ -1,10 +1,12 @@
 [interfaces.https.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo-only.
   [PaymentRequest interface: existence and properties of interface object]
     expected: FAIL
 
   [PaymentRequest interface object length]
     expected: FAIL
 
   [PaymentRequest interface object name]
     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 +1,7 @@
 [touch-retargeting.html]
   prefs: [dom.webcomponents.shadowdom.enabled:true]
+  disabled:
+    if not stylo: Shadow DOM is stylo only.
   [TouchEvent's touches, targetTouches, and changedTouches should be retargeted.]
     expected: FAIL