Support connecting to VM service via MessagePort / postMessage (#9964)

* Support connecting to a VM service over a MessagePort

Adds `?uri=messageport:<targetOrigin>`. On every connect, DevTools posts
a new `MessagePort` to `window.parent`, and the embedding page connects
it to a VM service. This lets pages such as DartPad, whose VM service
runs in a web worker, embed DevTools without a WebSocket.

* Address review feedback: validate targetOrigin, close port with null, and add connect timeout

* Close port on pagehide instead of unload
7 files changed
tree: 7bdb3c143f3a88ad20046874572760b18a50bb8a
  1. .agents/
  2. .gemini/
  3. .github/
  4. .vscode/
  5. _markdown_images/
  6. docs/
  7. packages/
  8. third_party/
  9. tool/
  10. .gitattributes
  11. .gitignore
  12. AGENTS.md
  13. analysis_options.yaml
  14. AUTHORS
  15. BETA_TESTING.md
  16. CLAUDE.md
  17. CODE_OF_CONDUCT.md
  18. CODEOWNERS
  19. CONTRIBUTING.md
  20. DEBUGGING.md
  21. devtools_options.yaml
  22. DOCUMENTATION.md
  23. flutter-candidate.txt
  24. LICENSE
  25. pubspec.lock
  26. pubspec.yaml
  27. README.md
  28. STYLE.md
  29. TESTING.md
  30. TRIAGE.md
README.md

Dart & Flutter DevTools

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