wangxianzhu@, could you take a look? Since you've changed clipDisplayItem file recently. 
Please feel free to reassign. 

Thanks!

ClusterFuzz has detected this issue as fixed in range 518061:518147.

Detailed report: https://clusterfuzz.com/testcase?key=6149877586460672

Fuzzer: mbarbella_js_mutation_layout
Job Type: linux_ubsan_vptr_content_shell_drt
Platform Id: linux

Crash Type: Bad-cast
Crash Address: 0x342c8fabc230
Crash State:
  Bad-cast to const blink::ClipDisplayItem from blink::DisplayItem
  blink::ClipDisplayItem::Equals
  blink::PaintController::CheckUnderInvalidation
  
Sanitizer: undefined (UBSAN)

Recommended Security Severity: High

Regressed: https://clusterfuzz.com/revisions?job=linux_ubsan_vptr_content_shell_drt&range=514498:517702
Fixed: https://clusterfuzz.com/revisions?job=linux_ubsan_vptr_content_shell_drt&range=518061:518147

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6149877586460672

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 6149877586460672 is verified as fixed, so closing issue as verified.

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

This bug has been closed for more than 14 weeks. Removing security view restrictions.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot