Bug 1624482 - Followup: Adapt to changes in bug 1590573. r=emalysz

Differential Revision: https://phabricator.services.mozilla.com/D70251

--HG--
extra : moz-landing-system : lando

toolkit/content/widgets/menulist.js

@@ -98,7 +98,7 @@
       }
 
       if (!this.hasAttribute("popuponly")) {
-        this.shadowRoot.appendChild(this.fragment);
+        this.shadowRoot.appendChild(this.constructor.fragment);
         this._labelBox = this.shadowRoot.getElementById("label-box");
         this._dropmarker = this.shadowRoot.querySelector("dropmarker");
         this.initializeAttributeInheritance();
@@ -111,15 +111,6 @@
       this.setInitialSelection();
     }
 
-    get fragment() {
-      if (!this.constructor.hasOwnProperty("_fragment")) {
-        this.constructor._fragment = MozXULElement.parseXULToFragment(
-          MozMenuList.markup
-        );
-      }
-      return document.importNode(this.constructor._fragment, true);
-    }
-
     // nsIDOMXULSelectControlElement
     set value(val) {
       // if the new value is null, we still need to remove the old value