Reland "[soft navs] Use a prefinalizer instead of UntracedMember for SoftNavigationContext"

This is a reland of commit 44f6a765b0170c296e5a61d9ed2e221b9e404138

The reland removes the always-failing Contains check called from the
prefinalizer [1], since it isn't needed with how we're currently
shutting down contexts. It also improves one of the GC tests, adding a
histogram expectation.

[1] https://chromium-review.googlesource.com/c/chromium/src/+/7256268/comment/4b3c1f8b_e8f4eab8/

Original change's description:
> [soft navs] Use a prefinalizer instead of UntracedMember for SoftNavigationContext
>
> SoftNavigationHeuristics does custom tracing of the set of contexts
> using UntracedMember. This used to be how we detect the set becoming
> empty, but we don't track this any longer. We do still, however, record
> some metrics and end a trace event, so I think we still need detect
> when soft nav contexts are disposed.
>
> This CL changes how we do this to use a prefinalizer instead, which is
> generally preferred to UntracedMember. This is being done to make set
> iteration safer, since HashSet entry erasure invalidates iterators,
> which would be a problem if a set interaction causes a GC, e.g. due to
> an allocation. This is a prerequisite for crrev.com/c/7120640, where I
> don't trust that an iteration I need to add is safe.
>
> Bug: 454082771, 454082773
> Change-Id: Id7932cf4f12f838c588aaf559053421bb494235a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7256268
> Commit-Queue: Scott Haseley <shaseley@chromium.org>
> Reviewed-by: Michal Mocny <mmocny@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1559010}

Bug: 454082771, 454082773
Change-Id: I7829a6d37749ece49ce82a3ae71ee55e839cf5c9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/7275266
Commit-Queue: Scott Haseley <shaseley@chromium.org>
Reviewed-by: Michal Mocny <mmocny@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1564582}
5 files changed
tree: 5d39f6d0a4415cf79a355d92c751ced4544c7e35
  1. .gemini/
  2. .github/
  3. agents/
  4. android_webview/
  5. apps/
  6. ash/
  7. base/
  8. build/
  9. build_overrides/
  10. buildtools/
  11. cc/
  12. chrome/
  13. chromecast/
  14. chromeos/
  15. codelabs/
  16. components/
  17. content/
  18. crypto/
  19. dbus/
  20. device/
  21. docs/
  22. extensions/
  23. fuchsia_web/
  24. gin/
  25. google_apis/
  26. gpu/
  27. headless/
  28. infra/
  29. ios/
  30. ipc/
  31. media/
  32. mojo/
  33. net/
  34. pdf/
  35. printing/
  36. remoting/
  37. rlz/
  38. sandbox/
  39. services/
  40. skia/
  41. sql/
  42. storage/
  43. styleguide/
  44. testing/
  45. third_party/
  46. tools/
  47. ui/
  48. url/
  49. webkit/
  50. .clang-format
  51. .clang-tidy
  52. .clangd
  53. .cursorignore
  54. .geminiignore
  55. .git-blame-ignore-revs
  56. .gitallowed
  57. .gitattributes
  58. .gitignore
  59. .gitmodules
  60. .gn
  61. .mailmap
  62. .rustfmt.toml
  63. .vpython3
  64. .yapfignore
  65. ATL_OWNERS
  66. AUTHORS
  67. BUILD.gn
  68. CODE_OF_CONDUCT.md
  69. codereview.settings
  70. CPPLINT.cfg
  71. CRYPTO_OWNERS
  72. DEPS
  73. DIR_METADATA
  74. LICENSE
  75. LICENSE.chromium_os
  76. OWNERS
  77. PRESUBMIT.py
  78. PRESUBMIT_test.py
  79. PRESUBMIT_test_mocks.py
  80. README.md
  81. SECURITY_OWNERS
  82. WATCHLISTS
README.md

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