[dds/dap] Don't handle isolate startup until isolate is in PauseStart state

While investigating the flaky test at https://github.com/dart-lang/sdk/issues/60187#issuecomment-3431336127 I found that we had two paths into `handleThreadStartup` - one which explicitly sent a "pause-on-entry" event, and one that did not. The method sets a flag so it only ever runs once.

This means depending on which instance of `handleThreadStartup` occurs, the client may or may not get the pause-on-entry event.

The case where it would is where the isolate already had a pause-start event when we found it. The case where it would not, is if the isolate did not have a pause event (for example it was None because the isolate was just being created).

I can't come up with a good explanation for why we would try to pre-emptively run startup for an isolate we just discovered with no pauseEvent, so I have removed this branch on the assumption that we would always then see a `PauseStart` event for the isolate and then handled it through the same code path (and therefore, always sent the `pause-on-entry` event prior to calling readyToResume).

Fixes https://github.com/dart-lang/sdk/issues/60187

Change-Id: I213e9865480942b074d4d8470703377ea7ddb519
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/457040
Reviewed-by: Helin Shiah <helinx@google.com>
Commit-Queue: Ben Konyi <bkonyi@google.com>
Reviewed-by: Ben Konyi <bkonyi@google.com>
4 files changed
tree: 96dc6a9cb77c319fea971040245c916bafb64a8b
  1. .dart_tool/
  2. .github/
  3. benchmarks/
  4. build/
  5. docs/
  6. pkg/
  7. runtime/
  8. samples/
  9. sdk/
  10. tests/
  11. third_party/
  12. tools/
  13. utils/
  14. .clang-format
  15. .gitattributes
  16. .gitconfig
  17. .gitignore
  18. .gn
  19. .mailmap
  20. .style.yapf
  21. AUTHORS
  22. BUILD.gn
  23. CHANGELOG.md
  24. codereview.settings
  25. CONTRIBUTING.md
  26. DEPS
  27. LICENSE
  28. OWNERS
  29. PATENT_GRANT
  30. PRESUBMIT.py
  31. pubspec.yaml
  32. README.dart-sdk
  33. README.md
  34. sdk.code-workspace
  35. sdk_args.gni
  36. sdk_packages.yaml
  37. SECURITY.md
  38. WATCHLISTS
README.md

Dart

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