Version: 51.0.2704.37
OS: CrOS 8172.25.0 (Official Build) beta-channel Chell

What steps will reproduce the problem?
(1) Go to a video site
(2) Plug headphones in
(3) Sound comes from speaker, not headphones

What is the expected output?

Sound comes from headphones

What do you see instead?

Sound comes from speaker.

Please use labels and text to provide additional information.

This was certainly working last week, so it seems like a recent regression.