UserAgent: Mozilla/5.0 (X11; CrOS x86_64 11151.59.0) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/71.0.3578.94 Safari/537.36
Platform: 11151.59.0 (Official Build) beta-channel nocturne

Example URL:

Steps to reproduce the problem:
1. Connect a USB Multichannel audio controller 
2. Launch a supported app like djay 2 or WeDJ from Google Play
3. The apps should recognize the supported controller and you should have 4 audio channels working from the controller.

What is the expected behavior?
The apps should recognize the supported midi controller and you should have 4 audio channels working from the midi controller.

What went wrong?
This feature was added in M67 and was working in M69 with the Reloop Beatpad controller and the Pioneer Wego4 controller + the Djay 2 app from the play store. I tested this on the Pixelbook M69.

It no longer works as of M70 and now M71 on both the Pixelbook and Pixel Slate (running Android 7.1 and Android 9). Connecting the controller is not recognized by the app. CroS can see the controller as a single audio device.
Also tested with with the WeDJ app from the play store. Same result. In fact Djay 2 badly hangs since M70 and it's not due to the app as it runs fine on Android and used to run on ChromeOS. It was even demoed by Google here: https://www.youtube.com/watch?v=6kIZ_u4QE9U (8:15 mark).

Did this work before? Yes M67

Is it a problem with Flash or HTML5? N/A

Does this work in other browsers? N/A

Chrome version: 71.0.3578.94  Channel: beta
OS Version: 11151.59.0
Flash Version: 

Contents of chrome://gpu: 

If any logs are needed, please let me know how to send them to you.