Backed out changeset c1561409e431 (bug 1466833) for permafailing on browser/components/search/test/browser_oneOffHeader.js on a CLOSED TREE

browser/components/search/content/search.xml

@@ -1291,12 +1291,6 @@
       <field name="_contextEngine">null</field>
 
       <constructor><![CDATA[
-        // Force the <deck> Custom Element to be constructed. This can be removed
-        // once Bug 1470242 makes this happen behind the scenes.
-        if (window.customElements) {
-          customElements.upgrade(document.getAnonymousElementByAttribute(this, "anonid", "search-panel-one-offs-header"));
-        }
-
         // Prevent popup events from the context menu from reaching the autocomplete
         // binding (or other listeners).
         let menu = document.getAnonymousElementByAttribute(this, "anonid", "search-one-offs-context-menu");