It's chromecast mirroring!!!!
I thought it was because of an Xposed module but when I try to mirror the screen an error Toast Notification appears, and thanks to an Xposed module I can see that the notification is sent by Google Play Services.
So I assume that it is a built in function.
Am I correct?
In the screenshots attached you the browser is open, but the tile is always there..
Unfortunately I didn't managed to letting it working..