Find it and CL did not provide any possible suspects.
Using Code Search for the file, "audio_manager.cc" assigning to the concern owner,
Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/c8569a7cd8c3cb6f9cd22467e084860721ceadd7

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

the warnings have nothing to do with the CHECK failure, it simply means that chrome tries to create multiple AudioManager.

Through code search on file SelectionEditor.cpp, suspected CL is
https://chromium.googlesource.com/chromium/src/+/14076c954628a8dc4bdefbd080cb80851d43d4ac

ClusterFuzz has detected this issue as fixed in range 450347:450395.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=5821767118749696

Fuzzer: bj_broddelwerk
Job Type: linux_debug_chrome
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  m_selectionInFlatTree.isValidFor(document()). VisibleSelection() in SelectionEdi
  blink::SelectionEditor::updateIfNeeded
  blink::FrameSelection::updateIfNeeded
  
Sanitizer: address (ASAN)

Regressed: https://cluster-fuzz.appspot.com/revisions?job=linux_debug_chrome&range=431812:431813
Fixed: https://cluster-fuzz.appspot.com/revisions?job=linux_debug_chrome&range=450347:450395

Reproducer Testcase: https://cluster-fuzz.appspot.com/download/AMIfv96O7JLA8-7YXJokAcVhF2apuqvn9J5ynWjO0_G4DlGMhd7bsUiNZ2HdZEWRjCPHsaYiH4tK0-VhAeRWIzvcXhR7M-inpd2ibGQoG1J1EdIBhF0X5yDLOF2QmxCxrNmdd7NqrPxAeeDHwKyklfTFA4MfPx33aqOue2RrA5lFM7owLjPm0mI?testcase_id=5821767118749696


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 5821767118749696 is verified as fixed, so closing issue.

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

ClusterFuzz has detected this issue as fixed in range 450347:450395.

Detailed report: https://cluster-fuzz.appspot.com/testcase?key=5821767118749696

Fuzzer: bj_broddelwerk
Job Type: linux_debug_chrome
Platform Id: linux

Crash Type: CHECK failure
Crash Address: 
Crash State:
  m_selectionInFlatTree.isValidFor(document()). VisibleSelection() in SelectionEdi
  blink::SelectionEditor::updateIfNeeded
  blink::FrameSelection::updateIfNeeded
  
Sanitizer: address (ASAN)

Regressed: https://cluster-fuzz.appspot.com/revisions?job=linux_debug_chrome&range=431812:431813
Fixed: https://cluster-fuzz.appspot.com/revisions?job=linux_debug_chrome&range=450347:450395

Reproducer Testcase: https://cluster-fuzz.appspot.com/download/AMIfv96O7JLA8-7YXJokAcVhF2apuqvn9J5ynWjO0_G4DlGMhd7bsUiNZ2HdZEWRjCPHsaYiH4tK0-VhAeRWIzvcXhR7M-inpd2ibGQoG1J1EdIBhF0X5yDLOF2QmxCxrNmdd7NqrPxAeeDHwKyklfTFA4MfPx33aqOue2RrA5lFM7owLjPm0mI?testcase_id=5821767118749696


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.