Predator and CL did not provide any possible suspects.
Using Code Search for the file, "midi_service.cc" assigning to the concern owner.

Suspecting Commit#
https://chromium.googlesource.com/chromium/src/+/0492fc281b7eb603be6e7f3f00afb7d9802ef3d5

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

This happens only on receiving an IPC in an unexpected order, e.g., receiving MidiHostMsg_SendData after MidiHostMsg_EndSession.

So, let me reprioritize this.

Also note that this should not be platform specific.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/78f5e86e47e0d85ff9a2d8fd097767f6be8b7997

commit 78f5e86e47e0d85ff9a2d8fd097767f6be8b7997
Author: Takashi Toyoshima <toyoshim@google.com>
Date: Fri Aug 18 12:58:48 2017

Web MIDI: make the MidiService robust against illegal ipc sequences

Now the MidiService raises a check failure when an illegal ipc
sequence is detected. But to run with ipc fuzzer, it should be
robust against such illegal ipc sequences rather than raising a
check failure.

BUG= 746969 ,  750011 ,  747662 

Change-Id: Ica788bd5371b2352a011a5d40037ef7e0da3ee48
Reviewed-on: https://chromium-review.googlesource.com/605156
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Takashi Toyoshima <toyoshim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#495533}
[modify] https://crrev.com/78f5e86e47e0d85ff9a2d8fd097767f6be8b7997/media/midi/midi_service.cc

ClusterFuzz has detected this issue as fixed in range 495531:495551.

Detailed report: https://clusterfuzz.com/testcase?key=5086352982147072

Fuzzer: ipc_fuzzer_gen
Job Type: linux_asan_chrome_ipc
Platform Id: linux

Crash Type: Null-dereference READ
Crash Address: 0x000000000000
Crash State:
  midi::MidiService::DispatchSendMidiData
  bool IPC::MessageT<MidiHostMsg_SendData_Meta, std::__1::tuple<unsigned int, std:
  content::MidiHost::OnMessageReceived
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=linux_asan_chrome_ipc&range=488146:488166
Fixed: https://clusterfuzz.com/revisions?job=linux_asan_chrome_ipc&range=495531:495551

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5086352982147072

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 has detected this issue as fixed in range 495531:495551.

Detailed report: https://clusterfuzz.com/testcase?key=5086352982147072

Fuzzer: ipc_fuzzer_gen
Job Type: linux_asan_chrome_ipc
Platform Id: linux

Crash Type: Null-dereference READ
Crash Address: 0x000000000000
Crash State:
  midi::MidiService::DispatchSendMidiData
  bool IPC::MessageT<MidiHostMsg_SendData_Meta, std::__1::tuple<unsigned int, std:
  content::MidiHost::OnMessageReceived
  
Sanitizer: address (ASAN)

Regressed: https://clusterfuzz.com/revisions?job=linux_asan_chrome_ipc&range=488146:488166
Fixed: https://clusterfuzz.com/revisions?job=linux_asan_chrome_ipc&range=495531:495551

Reproducer Testcase: https://clusterfuzz.com/download?testcase_id=5086352982147072

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.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b5985781e77b51eab38ef967c0f4466401fd80fd

commit b5985781e77b51eab38ef967c0f4466401fd80fd
Author: Takashi Toyoshima <toyoshim@google.com>
Date: Mon Aug 21 12:08:09 2017

Web MIDI: Check valid clients in MidiManager

MidiService had a |active_clients_| to detect when it destructs
MidiManager instance, but since MidiManager has a complete set
of active clients, it would be simple and safe to ask MidiManager
to check if there is at least one active client.

Bug:  746969 ,  750011 ,  747662 
Change-Id: I1491df4bc4b20c2605c979babb11e813d25702e4
Reviewed-on: https://chromium-review.googlesource.com/622294
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Takashi Toyoshima <toyoshim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#495918}
[modify] https://crrev.com/b5985781e77b51eab38ef967c0f4466401fd80fd/media/midi/midi_manager.cc
[modify] https://crrev.com/b5985781e77b51eab38ef967c0f4466401fd80fd/media/midi/midi_manager.h
[modify] https://crrev.com/b5985781e77b51eab38ef967c0f4466401fd80fd/media/midi/midi_service.cc
[modify] https://crrev.com/b5985781e77b51eab38ef967c0f4466401fd80fd/media/midi/midi_service.h