Predator and CL did not provide any possible suspects.
Using Code Search for the file, "FormatBlockCommand.cpp" assigning to the concern owner.
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/b66326f26629d4e161ad020ea34052c3f52598af

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

Lower to Pri-3, since real world usage of "FormatBlock" with  -webkit-appearance:searchfield is low.

ClusterFuzz has detected this issue as fixed in range 489151:489186.

Detailed report: https://clusterfuzz.com/testcase?key=4911553358069760

Fuzzer: inferno_layout_test_unmodified
Job Type: windows_asan_chrome
Platform Id: windows

Crash Type: Null-dereference READ
Crash Address: 0x00000018
Crash State:
  blink::CompositeEditCommand::CloneParagraphUnderNewElement
  blink::CompositeEditCommand::MoveParagraphWithClones
  blink::FormatBlockCommand::FormatRange
  
Sanitizer: address (ASAN)

Fixed: https://clusterfuzz.com/revisions?job=windows_asan_chrome&range=489151:489186

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=4911553358069760


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 4911553358069760 is verified as fixed, so closing issue as verified.

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