Add WebSocket context cleanup steps to support BFCache

[llannasatoll]

This allows pages with active WebSockets to enter the BFCache by removing the step that marks the document as unsalvageable.

Mirroring the WebTransport integration, the user agent now invokes the WebSocket context cleanup steps (to be added in whatwg/websockets#74) on BFCache entry. This triggers a connection failure, which queues a task to fire error and close events that are dispatched only after the page is restored from the BFCache.

• At least two implementers are interested (and none opposed):
  • Chromium
  • WebKit
• Tests are written and can be reviewed and commented upon at:
  • https://chromium-review.git.corp.google.com/c/chromium/src/+/7698838
• Implementation bugs are filed:
  • Chromium: https://issues.chromium.org/issues/467838624
  • Gecko: …
  • WebKit: …
  • Deno (only for timers, structured clone, base64 utils, channel messaging, module resolution, web workers, and web storage): …
  • Node.js (only for timers, structured clone, base64 utils, channel messaging, and module resolution): …
• Corresponding HTML AAM & ARIA in HTML issues & PRs:
• MDN issue is filed: …
• The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

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/document-lifecycle.html ( diff )
/infrastructure.html ( diff )