Bug 1633968 - Use TabContextMenu.contextTab in ext-menus r=rpl

Differential Revision: https://phabricator.services.mozilla.com/D73256

browser/components/extensions/parent/ext-menus.js

@@ -1181,11 +1181,7 @@ const menuTracker = {
       gMenuBuilder.build({ menu, tab, pageUrl, inToolsMenu: true });
     }
     if (menu.id === "tabContextMenu") {
-      let trigger = menu.triggerNode;
-      while (trigger && trigger.localName != "tab") {
-        trigger = trigger.parentNode;
-      }
-      const tab = trigger || tabTracker.activeTab;
+      const tab = menu.ownerGlobal.TabContextMenu.contextTab;
       const pageUrl = tab.linkedBrowser.currentURI.spec;
       gMenuBuilder.build({ menu, tab, pageUrl, onTab: true });
     }