How to show a progress icon during WebGL initialization?

Is there a way to keep the unity loading bar visible while a WebGL game initializes?

When a webGL game loads up… there is a very long pause after the loading bar where it is just a grey screen. I don’t understand why the Unity loading bar doesn’t just stay while the initialization or decompressing is happening. I’m not familiar with javascript or editing the web templates. A quick pointer would be appreciated.

I have found this amazing Blog post with examples. Comments say it will not work with Unity 5.6. But it may be a big step forward toward a complete solution: