On webpages that are expected to load slowly, stop loading of non-critical resources. This includes (but is not limited to) JavaScript and CSS resources that do not contribute significantly to the visual appearance. This would be limited to only the data saver users. Users are shown a Lite Mode UI in the omnibox. Users can load default behavior by tapping “Show original” in the omnibox UI. An intervention report is sent when this optimization occurs.
Docs: https://developers.google.com/web/updates/2018/09/reportingapi https://www.w3.org/TR/reporting/#intervention-report