Manual bisect:
Good build: 53.0.2783.2
Bad build: 53.0.2784.0

Narrow bisect URL:
https://chromium.googlesource.com/chromium/src/+log/814dd6ada11ce9b79feb7994a75d67c49d18ab63..849f8df4aa51c333cd14286b51673acc90e9b862?pretty=fuller&n=10000

Suspecting: r402853

Note: Issue is reproducible on Linux OS (14.04 LTS).

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Adding RB Label as this is a recent Regression. Please remove if not required.
Thank You.

Issue is still seen on the latest canary(54.0.2793.0) on Windows-7. Can we get an update on this issue.

This is not a media bug, it's either Blink or YouTube.

I cannot reproduce with a similar canary build, so I am assuming that this was a YouTube bug that has been fixed.

Please confirm if this is the case.

Okay, I was able to reproduce this with a more recent build. This makes me suspicious that it's not as simple as a specific commit, but something is indeed still broken.

It's difficult to see what exactly is going on since the menu disappears when you click in the inspector, but fundamentally it's just toggling an "area-checked" attribute on a <div> and there is CSS selecting for that. When broken it seems that the CSS is being applied totally incorrectly (eg. all of the menu items change their shade of white when toggling one checkbox).

Closing an re-opening the menu results in correct rendering, apparently without changing the HTML or CSS.

Suspecting CSS engine at this point, over to Blink>CSS for triage.

That should be "aria-checked" above.

cc'ing timloh@ for further debugging.

M53 beta launch is coming soon.Your bug is labelled as Beta ReleaseBlock, pls make sure to land the fix before 6:00 PM PST, Monday (07/18/16). Thank you.

Unable to repro this issue on Windows 7, MAC (10.11.5) & Ubuntu Trusty (14.04) for Google Chrome Canary Version - 54.0.2799.0 

Screen-recording is attached.

@vvishwakarma: Could you please update Chrome Canary to Latest Version - 54.0.2799.0 and let us know your observations.

Thank you.

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Did a bisect:

https://chromium.googlesource.com/chromium/src/+log/78d1ddce57dd1da3a9d166ebbfae758d32307185..849f8df4aa51c333cd14286b51673acc90e9b862

Probably this change: https://codereview.chromium.org/2141743002, fix has already been merged to M53 (see bug this is marked as a dupe of)