Switching to full-screen causes WebGL player freeze, and stays frozen even when switched back to windowed mode

Steps to Reproduce:
1. Open attached project or create a new project
2. Open Build Settings > WebGL
3. Switch Platform > Build & Run
4. Click on Full-Screen Button on the WebGL game

Actual Result:
Notice that the cube stops rotating due to freeze. Game freezes and stops working completely. No errors are thrown in console log

Expected Result:
WebGL player runs gracefully even if toggled to fullscreen

Reproducible on:
2019.1.0a11

Works on:
2019.1.0a10, 2018.3.0b12, 2018.3.0f1

Environment:
Windows and Mac

Note:
If the fullscreen button is pressed during splashscreen, an alert is thrown along with an error in console log. Find attached image to see error

Tested on browsers:
1. Google Chrome
2. Safari
3. Internet Explorer
4. Mozilla Firefox