UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.117 Safari/537.36

Steps to reproduce the problem:
1. Open https://webvr.info/samples/04-simple-mirroring.html
2. Click `Enter VR` to enter vr mode
3. Exit the vr mode
4. Click `Enter VR` to enter vr mode again

What is the expected behavior?
User should be able to enter into the VR mode without any problem

What went wrong?
1. The steam loading screen is displayed in the VR headset when user enters the vr mode second time
2. User can only enter the vr mode and use properly when the vr mode is enabled first time. VR mode can not be used after that.

Did this work before? Yes 67.0.3364.0

Does this work in other browsers? Yes

Chrome version: 68.0.3406.0  Channel: canary
OS Version: 10.0
Flash Version: 

I have tested with both vive & oculus HMD with SteamVR(version 1522946134). The issue persist in both HMD. The issue is not reproducible in Firefox. I have downloaded the old version from here: https://commondatastorage.googleapis.com/chromium-browser-snapshots/index.html?prefix=Win_x64/541279/