Predator and CL could not provide any possible suspects.
Using the code search for the file, “DocumentLoader.cpp” assigning to concern owner from GIT blame.

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/06d0ad12bb257b7da70bef82147d4890c5d49f33
@japhet  -- Could you please look into this issue, kindly reassign if it has nothing to do with your changes.
Thank You.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5484b52a5d8d14dfcf1e1e0457b3721f0e49c119

commit 5484b52a5d8d14dfcf1e1e0457b3721f0e49c119
Author: Nate Chapin <japhet@chromium.org>
Date: Mon Oct 02 22:04:01 2017

Don't let a child's unload detach in the middle of committing a javascript: url

Bug:  768167 
Test: fast/loader/navigate-during-javascript-url-commit.html
Change-Id: I4d02d38faeb877febd84b5ba800276c8be95d7ca
Reviewed-on: https://chromium-review.googlesource.com/671462
Commit-Queue: Nate Chapin <japhet@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#505810}
[add] https://crrev.com/5484b52a5d8d14dfcf1e1e0457b3721f0e49c119/third_party/WebKit/LayoutTests/fast/loader/navigate-during-javascript-url-commit-expected.txt
[add] https://crrev.com/5484b52a5d8d14dfcf1e1e0457b3721f0e49c119/third_party/WebKit/LayoutTests/fast/loader/navigate-during-javascript-url-commit.html
[add] https://crrev.com/5484b52a5d8d14dfcf1e1e0457b3721f0e49c119/third_party/WebKit/LayoutTests/fast/loader/resources/navigate-child-to-about-blank-in-grandchild-unload.html
[modify] https://crrev.com/5484b52a5d8d14dfcf1e1e0457b3721f0e49c119/third_party/WebKit/Source/core/loader/FrameLoader.cpp

ClusterFuzz has detected this issue as fixed in range 505750:505830.

Detailed report: https://clusterfuzz.com/testcase?key=5266684092088320

Fuzzer: inferno_twister
Job Type: windows_syzyasan_chrome
Platform Id: windows

Crash Type: Null-dereference
Crash Address: 0x0000005f
Crash State:
  blink::DocumentLoader::InstallNewDocument
  blink::DocumentLoader::ReplaceDocumentWhileExecutingJavaScriptURL
  blink::FrameLoader::ReplaceDocumentWhileExecutingJavaScriptURL
  
Memory Tool: SYZYASAN

Regressed: https://clusterfuzz.com/revisions?job=windows_syzyasan_chrome&range=503913:503932
Fixed: https://clusterfuzz.com/revisions?job=windows_syzyasan_chrome&range=505750:505830

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5266684092088320

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 5266684092088320 is verified as fixed, so closing issue as verified.

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