Predator and CL could not provide any possible suspects.
Using the code search for the file, “scrollbar_layer_delegate.cc” assigning to concern owner from GIT blame.
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/e6da4f138ccefccc641cdc28eb60622df779a1fc

@danakj  -- Could you please look into this issue, kindly reassign if it has nothing to do with your changes.
Thank You.

ClusterFuzz has detected this issue as fixed in range 574827:574829.

Detailed report: https://clusterfuzz.com/testcase?key=5085036785958912

Fuzzer: marty_html_twiddler
Job Type: linux_ubsan_vptr_content_shell_drt
Platform Id: linux

Crash Type: Null-dereference READ
Crash Address: 0x000000000000
Crash State:
  blink::ScrollbarLayerDelegate::PaintPart
  cc::PaintedScrollbarLayer::RasterizeScrollbarPart
  cc::PaintedScrollbarLayer::Update
  
Sanitizer: undefined (UBSAN)

Fixed: https://clusterfuzz.com/revisions?job=linux_ubsan_vptr_content_shell_drt&range=574827:574829

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5085036785958912

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.