I worked for a time on Google's internal videoconferencing platform, called GVC. This was in 2010-2011 at a time when a lot of the company's VC equipment was proprietary, specifically Cisco Tandberg units. These were expensive and would be expensive to roll out to thousands of meeting rooms.
around this time a different team was developing Hangouts. It's been awhile so my memory may be off but I think it was called Google Meet at the time? or maybe that was later? It's hard to keep track. I think Hangouts was the name adopted when Google+ came along and rolled Hangouts into its product offering.
There were different configurations of GVC but the most common were these All-in-One ("AIO") monitor/computer combos. It was a full Intel PC. So the GVC platform was a custom Linux distro. The system was designed so GVCs could talk to Google services, which was nontrivial, and so software updates could be rolled out. It kept old distros too in case one didn't boot. These GVCs had to be named and a whole bunch of other issues.
Additionally they needed support for various hardware like a touch panel to dial. Larger units required larger PTZ camera support and support for various microphones.
Anyway, Hangouts became the stack GVC was built on. This ultimately replaced virtually all Tandbergs and saved a fortune. This system was certainly still in use by 2017. I can't speak for later.
Monitoring was a part of all this. So when I see there are *.google.com specific APIs, we need to be sure we're talking about this accurately. Like can Google query any Chrome instance in the world? Or is it only from/to google.com? I don't know the answer and the Tweet doesn't specify.
But given the name hangouts_services and the domain restriction I consider it highly likely this is purely to support monitoring embedded Chrome for GVC. I could be wrong.