Predator and CL could not provide any possible suspects.
Using Code Search for the file, "LayoutBlock.cpp" assigning to the concern owner.

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/3a60b020bf35bc4ba48bf85e71acffd76de43360

@yoichio -- Could you please look into the issue, kindly re-assign if this is not related to your changes.
Thank You.

I'm not in the regressed range.

ClusterFuzz has detected this issue as fixed in range 497777:497807.

Detailed report: https://clusterfuzz.com/testcase?key=4974000680992768

Fuzzer: marty_html_twiddler
Job Type: windows_asan_content_shell
Platform Id: windows

Crash Type: Null-dereference READ
Crash Address: 0x00000014
Crash State:
  blink::LayoutBlock::AddChildBeforeDescendant
  blink::LayoutBlockFlow::AddChild
  blink::LayoutBlockFlow::AddChild
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=windows_asan_content_shell&range=497433:497463
Fixed: https://clusterfuzz.com/revisions?job=windows_asan_content_shell&range=497777:497807

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=4974000680992768

See https://github.com/google/clusterfuzz-tools for more information.

If you suspect that the result above is incorrect, try re-doing that job on the test case report page.

ClusterFuzz testcase 4974000680992768 is verified as fixed, so closing issue as verified.

If this is incorrect, please add ClusterFuzz-Wrong label and re-open the issue.