Map the webdx use counters to classic use counters for longer data history

[foolip]

Would there be interest in maintaining the mapping between web-features ID and the various Chrome use counters here?

This requires parsing at least these files from Chromium:
https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/public/mojom/use_counter/metrics/webdx_feature.mojom (simple cases)
https://source.chromium.org/chromium/chromium/src/+/main:components/page_load_metrics/browser/observers/use_counter/webdx_feature_maps.cc (use counters mapped from classic use counters, which have more historical data)
https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/public/mojom/use_counter/metrics/web_feature.mojom (needed to get the numeric ID of classic use counters)

[captainbrosset]

We have https://github.com/web-platform-dx/web-features-mappings/blob/main/mappings/chrome-use-counters.json, which is maintained by https://github.com/web-platform-dx/web-features-mappings/blob/main/scripts/update-chrome-use-counters-mapping.js

[foolip]

Alright, so the main thing that's missing that could be useful is the mapping from WebDX use counters to classic use counters. This would make it possible to link to old use counters with a much longer history where available.

For example, https://webstatus.dev/features/grid has data going back to 2024, but it's backed by https://chromestatus.com/metrics/feature/timeline/popularity/1693 which has data going back to 2017, showing the long arc of Grid adoption.