Affected versions

• Firefox 69.0b9 (20190726195447)
• Firefox 70.0a1 (20190729213839)

Affected platforms

• Windows 7x64
• Windows 10x64

Preconditions

• Disable hardware acceleration by setting layers.acceleration.disabled pref to true and restart the browser.

Steps to reproduce

1. Launch Firefox and go to https://www.crazygames.com/game/madalin-stunt-cars-2.

Expected result

• The game is loaded accordingly.

Actual result

• “Your browser does not support Madalin Stunt Cars 2. We recommend using the latest version of Chrome or Firefox.” error is presented or on another games the game loads and only the sound is played (no image is displayed).

Regression Range
Last good revision: 50fec259d5a66e44a087253fa5f9f805d32e8ef3 (2019-07-08)
First bad revision: 404680ad41e4e7d08aa46081a70095486f14e15f (2019-07-09)
Pushlog:
https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=50fec259d5a66e44a087253fa5f9f805d32e8ef3&tochange=404680ad41e4e7d08aa46081a70095486f14e15f

Additional Notes

• Attached a screenshot with the issue.

I see bug 1535373 in that regression range, wonder if it's related if they're doing some sort of capability check?

Setting the version flags to fix-optional to remove this dupe from triage.