UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/70.0.3538.77 Safari/537.36

Steps to reproduce the problem:
1. Go here https://pste.eu/p/9SEY.html
2. Click on `result` link on page before image below fully load

What is the expected behavior?
"PASS: history length is as expected" string appears.
Clicking on back button gets you to previous page with `result` link.

What went wrong?
"FAIL: history length is n, expected n+1" string appears.
Back button is disabled or gets you two pages back in actual history (depends on history size).

Did this work before? N/A 

Chrome version: 70.0.3538.77  Channel: stable
OS Version: 10.0
Flash Version: 

If before step 2 you wait for image to load or stop page loading by clicking on throbber button, history entry will be created as expected. 

Page from step 1 opens an iframe after click on link. Source site for this iframe opens target site in parent frame.

This minimal example pages simulate how Google Search works for user agents different than Chrome. Same behavior can be observed on Google Search when you artificially change user agent to different than Chrome (FF for example):

0. Set user agent to different than Chrome (e.g. by some extension),
1. Search for something,
2. Pick any entry fast, before Google Search fully load (you may need to limit your net speed),
3. Go back.
* May need several trials

Fails on stable and latest canary.

May be related to fix for this old webkit bug - https://bugs.webkit.org/show_bug.cgi?id=44086