UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36

Steps to reproduce the problem:
1. Plug in Xbox 360 wireless receiver 
2. Connect wireless gamepad
3. Try a call to navigator.getGamepads() or go to a site such as http://html5gamepad.com/
4. I expect to see a standard mapping on the Gamepad object, but don't.

What is the expected behavior?
The gamepad should be mapped to the "standard" mapping but isn't.

What went wrong?
My gamepad's ID is vendor 045e product 02a1, and it's a generic Microsoft Xbox 360 Wireless Controller. 

Take a look at the available mappings here: https://cs.chromium.org/chromium/src/device/gamepad/gamepad_standard_mappings_linux.cc?l=356

It looks like the gamepad is already supposed to be mapped in on line 361 but this apparently isn't happening because my controls are different than other controllers and the "mapping" entry in the Gamepad object isn't set to "standard".

Did this work before? No 

Does this work in other browsers? No
 Gamepad mapping doesn't seem to be implemented on Firefox at all.

Chrome version: 57.0.2987.133  Channel: stable
OS Version: 4.10.0-19-generic
Flash Version: 

The exact same controller/receiver works fine on Chrome on Windows.

Let me know if you need any additional information.