Find it and CL did not provide any possible suspect.
Using Code Search for the file, "Fullscreen.cpp" assigning to the concern owner
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/dd3989c829ddc1d3d36306143261278a20804229

@foolip -- 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 438498:440663.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=6399712539443200

Fuzzer: ifratric-browserfuzzer-v3
Job Type: mac_asan_chrome
Platform Id: mac

Crash Type: UNKNOWN READ
Crash Address: 0x0000000004e8
Crash State:
  blink::Fullscreen::eventQueueTimerFired
  blink::TimerBase::runInternal
  base::debug::TaskAnnotator::RunTask
  
Regressed: https://cluster-fuzz.appspot.com/revisions?job=mac_asan_chrome&range=419848:419954
Fixed: https://cluster-fuzz.appspot.com/revisions?job=mac_asan_chrome&range=438498:440663

Minimized Testcase (1.44 Kb): https://cluster-fuzz.appspot.com/download/AMIfv975jUsDcc5GE4mUs5zk_ycaeUmXfl2yCVoU31pdNKz-2a4xxUtSCjS8vKA6Ldlyq7LOjm9R2rCUpn89C-qrkYtWj1_-AlnYrWojWkXA8YwLrLL-jMDJF-9PkLkcjT_vOhsdtWWYrUepcYPlsVLEl5LYVeVVQw?testcase_id=6399712539443200

See https://dev.chromium.org/Home/chromium-security/bugs/reproducing-clusterfuzz-bugs 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 6399712539443200 is verified as fixed, so closing issue.

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