Expose Element.AttachShadow under dom.shadowdom.enabled pref

components/script/dom/element.rs

@@ -2642,6 +2642,13 @@ impl ElementMethods for Element {
         let doc = document_from_node(self);
         doc.enter_fullscreen(self)
     }
+
+    // XXX Hidden under dom.shadowdom.enabled pref. Only exposed to be able
+    //     to test partial Shadow DOM support for UA widgets.
+    // https://dom.spec.whatwg.org/#dom-element-attachshadow
+    fn AttachShadow(&self) -> Fallible<DomRoot<ShadowRoot>> {
+        self.attach_shadow()
+    }
 }
 
 impl VirtualMethods for Element {

components/script/dom/node.rs

@@ -23,7 +23,6 @@ use crate::dom::bindings::inheritance::{EventTargetTypeId, HTMLElementTypeId, No
 use crate::dom::bindings::inheritance::{SVGElementTypeId, SVGGraphicsElementTypeId, TextTypeId};
 use crate::dom::bindings::reflector::{reflect_dom_object, DomObject};
 use crate::dom::bindings::root::{Dom, DomRoot, DomSlice, LayoutDom, MutNullableDom};
-use crate::dom::shadowroot::ShadowRoot;
 use crate::dom::bindings::str::{DOMString, USVString};
 use crate::dom::bindings::xmlname::namespace_from_domstring;
 use crate::dom::characterdata::{CharacterData, LayoutCharacterDataHelpers};
@@ -51,6 +50,7 @@ use crate::dom::mutationobserver::{Mutation, MutationObserver, RegisteredObserve
 use crate::dom::nodelist::NodeList;
 use crate::dom::processinginstruction::ProcessingInstruction;
 use crate::dom::range::WeakRangeVec;
+use crate::dom::shadowroot::ShadowRoot;
 use crate::dom::svgsvgelement::{LayoutSVGSVGElementHelpers, SVGSVGElement};
 use crate::dom::text::Text;
 use crate::dom::virtualmethods::{vtable_for, VirtualMethods};

components/script/dom/webidls/Element.webidl

@@ -81,6 +81,8 @@ interface Element : Node {
   void insertAdjacentText(DOMString where_, DOMString data);
   [CEReactions, Throws]
   void insertAdjacentHTML(DOMString position, DOMString html);
+
+  [Throws, Pref="dom.shadowdom.enabled"] ShadowRoot attachShadow();
 };
 
 // http://dev.w3.org/csswg/cssom-view/#extensions-to-the-element-interface