UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.76 Safari/537.36

Example URL:
http://codepen.io/36degrees/pen/JEpYrr

Steps to reproduce the problem:
1. Add a new element to the DOM in response to a scroll event.

What is the expected behavior?
The new element should appear without affecting the browser's scroll offset.

What went wrong?
The scroll offset is shifted by the height of the introduced element, causing a 'jump' for the end user.

Does it occur on multiple sites: Yes

Is it a problem with a plugin? No 

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 56.0.2924.76  Channel: stable
OS Version: OS X 10.11.6
Flash Version: Shockwave Flash 24.0 r0

The linked code pen is a simplified test case based on behaviour seen at http://webarchive.nationalarchives.gov.uk/20161126131022/https://www.gov.uk/service-manual/agile-delivery/agile-government-services-introduction – where the introduction of a 'shim' element when making an element `position: fixed`causes a jump in the page.

This behaviour was not seen in Chrome 55.