I hoped that it was just an extension, but it is in fact an app. If you go to the app launcher tab (app launcher for taskbar is another thing Google killed lately) and right click Videostream, it says app info. It's really confusing, but I think all apps are extensions, but not all extensions are apps.

Came here to ask this.

After pairing the Android app on my Nexus 6P running December update, to my computer running Windows 10 Pro desktop, I noticed one of my cores was always at 100%. When I killed the chrome tab using that process, the videostream crash notice popped up. Restarting it stopped the high usage for a time, but it always came back. Unpairing seems to have fixed it. I can provide more details if you need.