Reapply "Fix OptionList iterating before beginning"

The new test in the original patch was failing on a Linux UBSan bot,
which revealed that OptionListIterator::operator*() was dereferencing a
null element. I fixed this by adjusting the test and adding a DCHECK to
make sure the element is not null before dereferencing. I also added a
WPT to make sure that the DCHECK doesn't get hit.

This reverts commit 3bef4696dcb69725d3f1c72a0984ba91c2e00056.
Original patch: commit 505729eedfd6243a6520d9fd09012b5dde449511

Fixed: 388299752
Change-Id: I01712fec0479ca567121051b33e6478cf77818b7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6203424
Commit-Queue: Traian Captan <tcaptan@chromium.org>
Auto-Submit: Joey Arhar <jarhar@chromium.org>
Reviewed-by: Traian Captan <tcaptan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1412393}
5 files changed
tree: 799c2131cf7ea961b8155e3848e47eea36bca44a
  1. android_webview/
  2. apps/
  3. ash/
  4. base/
  5. build/
  6. build_overrides/
  7. buildtools/
  8. cc/
  9. chrome/
  10. chromecast/
  11. chromeos/
  12. codelabs/
  13. components/
  14. content/
  15. crypto/
  16. dbus/
  17. device/
  18. docs/
  19. extensions/
  20. fuchsia_web/
  21. gin/
  22. google_apis/
  23. gpu/
  24. headless/
  25. infra/
  26. ios/
  27. ipc/
  28. media/
  29. mojo/
  30. native_client_sdk/
  31. net/
  32. pdf/
  33. ppapi/
  34. printing/
  35. remoting/
  36. rlz/
  37. sandbox/
  38. services/
  39. skia/
  40. sql/
  41. storage/
  42. styleguide/
  43. testing/
  44. third_party/
  45. tools/
  46. ui/
  47. url/
  48. webkit/
  49. .clang-format
  50. .clang-tidy
  51. .clangd
  52. .git-blame-ignore-revs
  53. .gitallowed
  54. .gitattributes
  55. .gitignore
  56. .gitmodules
  57. .gn
  58. .mailmap
  59. .rustfmt.toml
  60. .vpython3
  61. .yapfignore
  62. ATL_OWNERS
  63. AUTHORS
  64. BUILD.gn
  65. CODE_OF_CONDUCT.md
  66. codereview.settings
  67. CPPLINT.cfg
  68. CRYPTO_OWNERS
  69. DEPS
  70. description
  71. DIR_METADATA
  72. LICENSE
  73. LICENSE.chromium_os
  74. OWNERS
  75. PRESUBMIT.py
  76. PRESUBMIT_test.py
  77. PRESUBMIT_test_mocks.py
  78. README.md
  79. WATCHLISTS
README.md

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