UserAgent: Mozilla/5.0 (Windows NT 6.3; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2926.0 Safari/537.36

Steps to reproduce the problem:
1. Read illuminance value with below very simple code:
  > let s = new AmbientLightSensor();
  > s.onchange = () => console.log(s.reading.illuminance); s.start();
2. Change the ambient light illuminance of the device

What is the expected behavior?
The "s.reading.illuminance" changes with the ambient light illuminance of the device change.

What went wrong?
The value of "s.reading.illuminance" is always zero.
This issue is only reproduced on Windows.

Did this work before? N/A 

Does this work in other browsers? N/A

Chrome version: 57.0.2926.0  Channel: canary
OS Version: 6.3
Flash Version: Shockwave Flash 24.0 r0