Predator and CL did not provide any possible suspects.
Using Code Search for the file, "axobjectcacheimpl.cpp" assignined to concern owner.
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/1b5b587f547319a4dc72d06fc25b0494826fd9cd

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

This is beyond me, and I don't think my change caused it.

Here's what I think happens (from staring at call stacks and tracing code):
1) There's a LayoutMenuList open
2) Someone closes, or causes an ImplicitClose for the Document
3) A JS handler responds to this by calling setOuterHtml
4) Active menu option is now being removed?
5) AXMenuList::DidUpdateActiveOption(int option_index) runs, without checking if the document is still valid
6) Blam accesing the (gone) document's AXObjectCache 

ClusterFuzz has detected this issue as fixed in range 488838:488849.

Detailed report: https://clusterfuzz.com/testcase?key=4574714701021184

Fuzzer: inferno_layout_test_unmodified
Job Type: windows_syzyasan_content_shell
Platform Id: windows

Crash Type: Null-dereference
Crash Address: 0x0000004f
Crash State:
  WTF::HashTable<blink::Member<blink::ModuleScript>,blink::Member<blink::ModuleScr
  blink::AXObjectCacheImpl::GenerateAXID
  blink::AXObjectCacheImpl::GetOrCreateAXID
  
Memory Tool: SYZYASAN

Regressed: https://clusterfuzz.com/revisions?job=windows_syzyasan_content_shell&range=483471:483525
Fixed: https://clusterfuzz.com/revisions?job=windows_syzyasan_content_shell&range=488838:488849

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=4574714701021184


Additional requirements: Requires Gestures

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 4574714701021184 is verified as fixed, so closing issue as verified.

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