Expose contentEncoding in resourceTiming

[guohuideng2024]

こんにちは TAG-さん!

I'm requesting a TAG review of exposing contentEncoding in resourceTiming.

Propose that we add an explicit .contentEncoding in resourceTiming.
contentEncoding value has been very helpful for web apps and CDN in monitoring and optimization. As more compressions are deployed, it's no longer practical to infer such value. Therefore, it's desirable to explicitly expose it.

• Explainer¹:
  https://github.com/guohuideng2024/resource-timing/blob/gh-pages/Explainers/Content_Encoding.md
• Specification:
  Return a content-encoding header for resource timing and more whatwg/fetch#1796
  Expose a filtered content-encoding value to resource timing  w3c/resource-timing#411
• WPT Tests:
  https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/web_tests/external/wpt/resource-timing/content-encoding.https.html
• User research: Here.
• Security and Privacy self-review²: Here.
• GitHub repo:
  https://github.com/w3c/resource-timing
• Primary contacts:
  @guohuideng2024, Microsoft
• Organization/project driving the specification: Microsoft
• Multi-stakeholder support³:
  • Chromium comments: Already implemented behind a feature flag.
  • Mozilla comments: Expose contentEncoding in resourceTiming mozilla/standards-positions#1189
  • WebKit comments: expose contentEncoding in resourceTiming WebKit/standards-positions#467
• Status/issue trackers for implementations⁴:
  https://chromestatus.com/feature/4818080273006592
  Expose Content-Encoding to ResourceTiming w3c/resource-timing#381

Further details:

• I have reviewed the TAG's Web Platform Design Principles
• The group where the work on this specification is currently being done: WebPerfWG
• The group where standardization of this work is intended to be done (if different from the current group): WebPerfWG
• Major unresolved issues with or opposition to this specification: None.
• This work is being funded by: Microsoft