Bug 1849674 - Remove dom.shadowdom.slot.assign.enabled pref r=smaug

Differential Revision: https://phabricator.services.mozilla.com/D186675

dom/html/HTMLSlotElement.cpp

@@ -169,7 +169,6 @@ const nsTArray<nsINode*>& HTMLSlotElement::ManuallyAssignedNodes() const {
 }
 
 void HTMLSlotElement::Assign(const Sequence<OwningElementOrText>& aNodes) {
-  MOZ_ASSERT(StaticPrefs::dom_shadowdom_slot_assign_enabled());
   nsAutoScriptBlocker scriptBlocker;
 
   // no-op if the input nodes and the assigned nodes are identical

dom/webidl/Element.webidl

@@ -274,7 +274,6 @@ partial interface Element {
 dictionary ShadowRootInit {
   required ShadowRootMode mode;
   boolean delegatesFocus = false;
-  [Pref="dom.shadowdom.slot.assign.enabled"]
   SlotAssignmentMode slotAssignment = "named";
 };
 

dom/webidl/HTMLSlotElement.webidl

@@ -18,7 +18,6 @@ interface HTMLSlotElement : HTMLElement {
   [CEReactions, SetterThrows] attribute DOMString name;
   sequence<Node> assignedNodes(optional AssignedNodesOptions options = {});
   sequence<Element> assignedElements(optional AssignedNodesOptions options = {});
-  [Pref="dom.shadowdom.slot.assign.enabled"]
   undefined assign((Element or Text)... nodes);
 };
 

dom/webidl/ShadowRoot.webidl

@@ -25,7 +25,6 @@ interface ShadowRoot : DocumentFragment
   // Shadow DOM v1
   readonly attribute ShadowRootMode mode;
   readonly attribute boolean delegatesFocus;
-  [Pref="dom.shadowdom.slot.assign.enabled"]
   readonly attribute SlotAssignmentMode slotAssignment;
   readonly attribute Element host;
   attribute EventHandler onslotchange;

modules/libpref/init/StaticPrefList.yaml

@@ -4546,12 +4546,6 @@
   value: @IS_NOT_ANDROID@
   mirror: always
 
-# Is the 'assign' API for slot element enabled?
-- name: dom.shadowdom.slot.assign.enabled
-  type: bool
-  value: true
-  mirror: always
-
 # NOTE: This preference is used in unit tests. If it is removed or its default
 # value changes, please update test_sharedMap_static_prefs.js accordingly.
 - name: dom.webcomponents.shadowdom.report_usage