Predator and CL did not provide any possible suspects.
Using Code Search for the file, "navigation_controller_impl.cc" assigning to the concern owner.

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/eaace7813ae608e491f7aa502b08da57b32ce0bc

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

ClusterFuzz has detected this issue as fixed in range 491035:491089.

Detailed report: https://clusterfuzz.com/testcase?key=5323304096497664

Fuzzer: ipc_fuzzer_gen
Job Type: linux_asan_chrome_ipc_32bit
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  !in_navigate_to_pending_entry_ || delegate_->IsBeingDestroyed() in navigation_co
  content::NavigationControllerImpl::DiscardNonCommittedEntries
  content::WebContentsImpl::OnDialogClosed
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=linux_asan_chrome_ipc_32bit&range=490505:490547
Fixed: https://clusterfuzz.com/revisions?job=linux_asan_chrome_ipc_32bit&range=491035:491089

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5323304096497664


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 5323304096497664 is verified as fixed, so closing issue as verified.

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