Per an 11 November 2019 post on the Chromium Blog by Addy Osmani, Ben Greenstein and Bryan McQuade says in part:
"In the future, Chrome may identify sites that typically load fast or slow for users with clear badging. This may take a number of forms and we plan to experiment with different options, to determine which provides the most value to our users.
"Badging is intended to identify when sites are authored in a way that makes them slow generally, looking at historical load latencies. Further along, we may expand this to include identifying when a page is likely to be slow for a user based on their device and network conditions.
Note reference top "device and network conditions" - they're talking about mobile, for sure. (Remember Google is now "mobile first".)
Locations for these new fast/slow indicators that Google is considering include the loading screen, loading progress bar and context menu. (See the graphic above.)
Note also that this will only be the beginning of website labeling by Google:
"... Our long-term goal is to define badging for high-quality experiences, which may include signals beyond just speed..."
And best heed this advice too (emphasis added):
"We will publish updates to this plan as we approach future releases, but don’t wait to optimize your site..."
The post also includes helpful links to some Google resources for help in speeding up your site:
How fast is your site?