From 50c389b817e4b9ae242b27a9534100ff746a384f 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 - Disable smooth scroll on tabbar scrollbox to
 avoid stopping scrolling the last tab on race conditions. r=bgrins

Differential Revision: https://phabricator.services.mozilla.com/D33615

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

diff --git a/browser/base/content/test/tabs/browser_tabCloseSpacer.js b/browser/base/content/test/tabs/browser_tabCloseSpacer.js
index 62f4160a17fd..6d3eb906ec11 100644
--- a/browser/base/content/test/tabs/browser_tabCloseSpacer.js
+++ b/browser/base/content/test/tabs/browser_tabCloseSpacer.js
@@ -42,6 +42,12 @@ add_task(async function() {
 
 async function overflowTabs() {
   let arrowScrollbox = gBrowser.tabContainer.arrowScrollbox;
+  const originalSmoothScroll = arrowScrollbox.smoothScroll;
+  arrowScrollbox.smoothScroll = false;
+  registerCleanupFunction(() => {
+    arrowScrollbox.smoothScroll = originalSmoothScroll;
+  });
+
   let width = ele => ele.getBoundingClientRect().width;
   let tabMinWidth = parseInt(getComputedStyle(gBrowser.selectedTab, null).minWidth);
   let tabCountForOverflow = Math.ceil(width(arrowScrollbox) / tabMinWidth * 1.1);