1397252 - A horizontal scroll bar is wrongly displayed for a fraction of a second when opening/closing the Customization menu

Status: VERIFIED FIXED

(Firefox :: New Tab Page, defect)

Description

[Ciprian Muresan [:cmuresan], Formerly of Ecosystem QA - please needinfo @mcoman for things regarding the team]

Attachment: scroll bar is displayed for a second.gif

[Affected versions]:
- Firefox 57.0a1 Build ID 20170905220108

[Affected Platforms]:
- All Windows
- All Mac
- All Linux

[Prerequisites]:
- browser.newtabpage.activity-stream.enabled is set to true in about:config on a clean new profile.

[Steps to reproduce]:
1. Start the browser with the profile from prerequisites and open a New Tab.
2. Click the "Customize your New Tab page" button and observe the bottom part of the menu.
 
[Expected results]:
- The open animation is smooth.

[Actual results]:
- A horizontal scroll bar is displayed for a fraction of a second.

[Notes]:
- On Mac and Windows, the same scroll bar appears when you close the menu.
- On Ubuntu, there is an empty space in stead of a scroll bar.
- Attached a screen recording of the issue.

Comment 1

[Ed Lee :Mardak]

Fixed by https://github.com/mozilla/activity-stream/pull/3363 to be uplifted via bug 1396609.

Comment 2

[Marius Coman [:mcoman], Ecosystem QA]

The horizontal scroll bar is no longer displayed when opening/closing the Customization menu.
Verified as fixed using latest Nightly 57.0a1 Build ID 20170915100121, on Windows 10 x64 and Mac 10.12.