Bug 1901769 - Make browser_test_clipboard_contextmenu.js work with native macOS context menus. r=fix

widget/tests/browser/browser_test_clipboard_contextmenu.js

@@ -45,8 +45,8 @@ async function waitForPasteContextMenu() {
 function promiseClickPasteButton() {
   info("Wait for clicking paste contextmenu");
   const pasteButton = document.getElementById(kPasteMenuItemId);
-  let promise = BrowserTestUtils.waitForEvent(pasteButton, "click");
-  EventUtils.synthesizeMouseAtCenter(pasteButton, {});
+  let promise = BrowserTestUtils.waitForEvent(pasteButton, "command");
+  document.getElementById(kPasteMenuPopupId).activateItem(pasteButton);
   return promise;
 }