UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/68.0.3440.84 Safari/537.36

Example URL:
https://store.steampowered.com/app/427520/Factorio/

Steps to reproduce the problem:
1. Go to chrome://flags/#out-of-blink-cors to enable out of blink CORS and restart the browser.
2. Go to a store.steampowered.com app page with a video.

What is the expected behavior?
The video plays.

What went wrong?
The video doesn't play.  The JavaScript console has a few errors like:

Failed to load https://steamcdn-a.akamaihd.net/steam/apps/256660595/movie480.webm?t=1455896504: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'https://store.steampowered.com' is therefore not allowed access.

Did this work before? N/A 

Chrome version: 68.0.3440.84  Channel: stable
OS Version: Fedora 28
Flash Version: 

Attached is a HAR file and a NetLog file of when the problem happened (both created at the same time from the same page refresh).

The only thing I've found that fixes the problem is disabling the out of blink CORS experiment.

Things that didn't fix the problem:

* Viewing the video under a brand new profile.
* Clearing all non-cookie site data with the devtool's application tab.
* Clearing the browser's entire cache.
 

Deleted: steam-net-export-log.json.bz2 35.3 KB

steam-net-export-log.json.bz2 35.3 KB Download

Deleted: steam.har.bz2 4.9 MB

steam.har.bz2 4.9 MB Download