Predator and CL could not provide any possible suspects.
Using Code Search for the file, "webm_audio_client.cc" assigning to the concern owner who might be related.

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/162236743c74fa040e822ea4d846215e4543791e

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

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/bbcbac2763e4d3bd5b1f3a627a89aa0fbfc87523

commit bbcbac2763e4d3bd5b1f3a627a89aa0fbfc87523
Author: flim <flim@chromium.org>
Date: Wed Aug 30 19:57:39 2017

Limit the number of discrete channels to (0, 32)

Bug:  760041 
Change-Id: Ic6c68c5a568177c0f701fc1befbe4a7391e1008e
Reviewed-on: https://chromium-review.googlesource.com/641903
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Felicia Lim <flim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#498579}
[modify] https://crrev.com/bbcbac2763e4d3bd5b1f3a627a89aa0fbfc87523/media/base/audio_decoder_config.cc

ClusterFuzz has detected this issue as fixed in range 498575:498629.

Detailed report: https://clusterfuzz.com/testcase?key=5428156160016384

Fuzzer: libFuzzer_mediasource_WEBM_VP9_pipeline_integration_fuzzer
Job Type: libfuzzer_chrome_ubsan
Platform Id: linux

Crash Type: Integer-overflow
Crash Address: 
Crash State:
  media::AudioDecoderConfig::SetChannelsForDiscrete
  media::WebMAudioClient::InitializeConfig
  media::WebMTracksParser::OnListEnd
  
Sanitizer: undefined (UBSAN)

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=497087:497155
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=498575:498629

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5428156160016384

See https://chromium.googlesource.com/chromium/src/+/master/testing/libfuzzer/reproducing.md 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 5428156160016384 is verified as fixed, so closing issue as verified.

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