From d427e7411c371fc6f85ca5bbdaab4b5185ffd97e Mon Sep 17 00:00:00 2001
From: Hiroyuki Ikezoe <hikezoe@mozilla.com>
Date: Mon, 10 Jun 2019 03:06:25 +0000
Subject: [PATCH] Bug 1488953 - Wait for a scrollend event to make sure the
 scrolling has finished before proceeding the test. r=bgrins

Differential Revision: https://phabricator.services.mozilla.com/D33614

--HG--
extra : moz-landing-system : lando
---
 browser/base/content/test/tabs/browser_tabCloseSpacer.js | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/browser/base/content/test/tabs/browser_tabCloseSpacer.js b/browser/base/content/test/tabs/browser_tabCloseSpacer.js
index 4142f8ef80fa..62f4160a17fd 100644
--- a/browser/base/content/test/tabs/browser_tabCloseSpacer.js
+++ b/browser/base/content/test/tabs/browser_tabCloseSpacer.js
@@ -48,7 +48,11 @@ async function overflowTabs() {
   while (gBrowser.tabs.length < tabCountForOverflow) {
     BrowserTestUtils.addTab(gBrowser, "about:blank", { skipAnimation: true, index: 0 });
   }
-  await window.promiseDocumentFlushed(() => {});
+
+  // Make sure scrolling finished.
+  await new Promise(resolve => {
+    arrowScrollbox.addEventListener("scrollend", resolve, { once: true });
+  });
 }
 
 function getLastCloseButton() {