Bug 1430408 - Part 2: Wait for the next event tick after transitionend event to make sure the all event handlers finish in devtools/client/debugger/test/mochitest/browser_dbg_instruments-pane-collapse_keyboard.js r=pbro

devtools/client/debugger/test/mochitest/browser_dbg_instruments-pane-collapse_keyboard.js

@@ -35,4 +35,8 @@ async function togglePane(button, message, pane, keycode) {
   button.focus();
   EventUtils.synthesizeKey(keycode, {});
   await onTransitionEnd;
+
+  // Wait for the next event tick to make sure all transitionend event
+  // handlers finish.
+  await waitForTick();
 }