Predator and CL could not provide any possible suspects.
Using the code search for the file, “mp4_stream_parser.cc” assigning to concern owner from GIT revision log.

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/f40f65fcd5154127ca5e7a354b2c3a2ba779d8bc

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

Thank You.

CL in review: https://chromium-review.googlesource.com/c/chromium/src/+/660778

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/01a1196369f223e75d1c2e1687397828ec346641

commit 01a1196369f223e75d1c2e1687397828ec346641
Author: Matt Wolenetz <wolenetz@chromium.org>
Date: Mon Sep 11 18:32:28 2017

MSE: Protect from run_start_dts overflow in mp4::TrackRunIterator::init

BUG= 763624 

Change-Id: I87bb033e5bc86ebaedb2eec815dcbc7aa1e10ff5
Reviewed-on: https://chromium-review.googlesource.com/660778
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Matthew Wolenetz <wolenetz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#500983}
[modify] https://crrev.com/01a1196369f223e75d1c2e1687397828ec346641/media/formats/mp4/track_run_iterator.cc

#3 should fix this. Pending CF verification...

ClusterFuzz has detected this issue as fixed in range 500968:501035.

Detailed report: https://clusterfuzz.com/testcase?key=6404897502396416

Fuzzer: libFuzzer_mediasource_MP4_AACLC_AVC_pipeline_integration_fuzzer
Job Type: libfuzzer_chrome_ubsan
Platform Id: linux

Crash Type: Integer-overflow
Crash Address: 
Crash State:
  media::mp4::TrackRunIterator::Init
  media::mp4::MP4StreamParser::ParseMoof
  media::mp4::MP4StreamParser::ParseBox
  
Sanitizer: undefined (UBSAN)

Regressed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=499820:499882
Fixed: https://clusterfuzz.com/revisions?job=libfuzzer_chrome_ubsan&range=500968:501035

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=6404897502396416

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 6404897502396416 is verified as fixed, so closing issue as verified.

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