UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:58.0) Gecko/20100101 Firefox/58.0

Steps to reproduce the problem:
1. Open https://tobireif.com/non_site_stuff/test-page_for_horizontal_scrolling_report/ .
2. Open the dev tools, turn on device mode, set the width of the "Responsive" area to 360.
3. Drag the page content to the left.

What is the expected behavior?
The page should not be scrollable horizontally.

What went wrong?
The page is scrollable horizontally. After you dragged the page to the left, note the white stripe on the right which remains after you ended dragging the page (also eg after you dragged the page to the right and back to the left).

Did this work before? N/A 

Does this work in other browsers? N/A

Chrome version: Version 64.0.3282.119 (Official Build) (64-bit)  Channel: stable
OS Version: OS X 10.13
Flash Version: 

When you inspect the page you'll see that the "html"-element is 360px wide with no padding/border/margins - thus the page should not be scrollable horizontally in the 360px wide viewport.

Seems to work in Safari / there's no horizontal scroll in Safari.