HTML search element with form functionality - specification and implementation draft

I’ve been working on the implementation and specification of the proposed <search> element, now I can share the drafts with you. I’m looking for feedback and code review from implementers and web developers. There are many days of work in it. Feel free to comment here, in the gists, the commits, or file issues in the rendered specification draft (see link in the bottom-right corner).

• Proposal, motivation, use-cases
• Implementation drafts (commits on GitHub):
  • Chromium
  • WebKit
  • Firefox in the queue
• Specification draft:
  • Readable form (rendered)
  • Changes
  • Breakdown of changes

Updated link: Proposal, motivation, use-cases

Implementation has been submitted for Chrome:
https://chromium-review.googlesource.com/c/chromium/src/+/3323365

Easier to read on GitHub: