Bug 1723396 - Ship Custom Elements disabledFeatures; r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D121491

dom/base/CustomElementRegistry.cpp

@@ -916,6 +916,7 @@ void CustomElementRegistry::Define(
       }
     }
 
+    if (StaticPrefs::dom_webcomponents_disabledFeatures_enabled()) {
       /**
        * 14.6. Let disabledFeatures be an empty sequence<DOMString>.
        * 14.7. Let disabledFeaturesIterable be Get(constructor,
@@ -925,7 +926,6 @@ void CustomElementRegistry::Define(
        *       disabledFeaturesIterable to a sequence<DOMString>.
        *       Rethrow any exceptions from the conversion.
        */
-    if (StaticPrefs::dom_webcomponents_formAssociatedCustomElement_enabled()) {
       if (!JSObjectToAtomArray(aCx, constructor, u"disabledFeatures"_ns,
                                disabledFeatures, aRv)) {
         return;
@@ -940,7 +940,9 @@ void CustomElementRegistry::Define(
       //        "shadow".
       disableShadow = disabledFeatures.Contains(
           static_cast<nsStaticAtom*>(nsGkAtoms::shadow));
+    }
 
+    if (StaticPrefs::dom_webcomponents_formAssociatedCustomElement_enabled()) {
       // 14.11. Let formAssociatedValue be Get(constructor, "formAssociated").
       //        Rethrow any exceptions.
       JS::Rooted<JS::Value> formAssociatedValue(aCx);

dom/base/Element.cpp

@@ -1139,9 +1139,7 @@ bool Element::CanAttachShadowDOM() const {
    */
   // It will always have CustomElementData when the element is a valid custom
   // element or has is value.
-  CustomElementData* ceData = GetCustomElementData();
-  if (StaticPrefs::dom_webcomponents_formAssociatedCustomElement_enabled() &&
-      ceData) {
+  if (CustomElementData* ceData = GetCustomElementData()) {
     CustomElementDefinition* definition = ceData->GetCustomElementDefinition();
     // If the definition is null, the element possible hasn't yet upgraded.
     // Fallback to use LookupCustomElementDefinition to find its definition.

modules/libpref/init/StaticPrefList.yaml

@@ -3704,6 +3704,12 @@
   value: false
   mirror: always
 
+# Is support for custom element disabledFeatures enabled?
+- name: dom.webcomponents.disabledFeatures.enabled
+  type: bool
+  value: true
+  mirror: always
+
 # Is support for form-associated custom element enabled?
 - name: dom.webcomponents.formAssociatedCustomElement.enabled
   type: bool

testing/web-platform/meta/shadow-dom/__dir__.ini

@@ -1 +0,0 @@
-prefs: [dom.webcomponents.formAssociatedCustomElement.enabled:true]