Stack Trace:
-------------
Thread 14 CRASHED [EXC_BAD_INSTRUCTION / EXC_I386_INVOP @ 0x000000010d7eb14f ] MAGIC SIGNATURE THREAD
Stack Quality78%Show frame trust levels
0x000000010d7eb14f	(Google Chrome Framework -lock.h )	midi::MidiService::EndSession(midi::MidiManagerClient*)
0x000000010b21aea5	(Google Chrome Framework -tuple.h:91 )	bool IPC::MessageT<MidiHostMsg_EndSession_Meta, std::__1::tuple<>, void>::Dispatch<content::MidiHost, content::MidiHost, void, void (content::MidiHost::*)()>(IPC::Message const*, content::MidiHost*, content::MidiHost*, void*, void (content::MidiHost::*)())
0x000000010b21a977	(Google Chrome Framework -midi_host.cc:82 )	content::MidiHost::OnMessageReceived(IPC::Message const&)
0x000000010af7a001	(Google Chrome Framework -browser_message_filter.cc:87 )	content::BrowserMessageFilter::Internal::OnMessageReceived(IPC::Message const&)
0x000000010cb162bc	(Google Chrome Framework -message_filter_router.cc:22 )	IPC::MessageFilterRouter::TryFilters(IPC::Message const&)
0x000000010cb07002	(Google Chrome Framework -ipc_channel_proxy.cc:88 )	IPC::ChannelProxy::Context::TryFilters(IPC::Message const&)
0x000000010cb07141	(Google Chrome Framework -ipc_channel_proxy.cc:123 )	IPC::ChannelProxy::Context::OnMessageReceived(IPC::Message const&)
0x000000010cb050fd	(Google Chrome Framework -ipc_channel_mojo.cc:414 )	IPC::ChannelMojo::OnMessageReceived(IPC::Message const&)
0x000000010cb0a79a	(Google Chrome Framework -ipc_message_pipe_reader.cc:110 )	IPC::internal::MessagePipeReader::Receive(std::__1::vector<unsigned char, std::__1::allocator<unsigned char> > const&, base::Optional<std::__1::vector<mojo::StructPtr<IPC::mojom::SerializedHandle>, std::__1::allocator<mojo::StructPtr<IPC::mojom::SerializedHandle> > > >)
0x000000010abf5ebf	(Google Chrome Framework -ipc.mojom.cc:262 )	IPC::mojom::ChannelStubDispatch::Accept(IPC::mojom::Channel*, mojo::Message*)
0x000000010cb0cd89	(Google Chrome Framework -ipc_mojo_bootstrap.cc:752 )	IPC::(anonymous namespace)::ChannelAssociatedGroupController::Accept(mojo::Message*)
0x000000010c61deaa	(Google Chrome Framework -connector.cc:256 )	mojo::Connector::ReadSingleMessage(unsigned int*)
0x000000010c61e150	(Google Chrome Framework -connector.cc:281 )	mojo::Connector::OnWatcherHandleReady(unsigned int)
0x000000010c62b6b3	(Google Chrome Framework -callback.h:85 )	mojo::Watcher::OnHandleReady(unsigned int)
0x000000010c56fb9f	(Google Chrome Framework -callback.h:68 )	base::debug::TaskAnnotator::RunTask(char const*, base::PendingTask*)
0x000000010c59446a	(Google Chrome Framework -message_loop.cc:423 )	base::MessageLoop::RunTask(base::PendingTask*)
0x000000010c5947bb	(Google Chrome Framework -message_loop.cc:434 )	base::MessageLoop::DeferOrRunPendingTask(base::PendingTask)
0x000000010c594b82	(Google Chrome Framework -message_loop.cc:527 )	base::MessageLoop::DoWork()
0x000000010c597334	(Google Chrome Framework -message_pump_libevent.cc:218 )	base::MessagePumpLibevent::Run(base::MessagePump::Delegate*)
0x000000010c5b60f2	(Google Chrome Framework -run_loop.cc:37 )	base::RunLoop::Run()
0x000000010b061293	(Google Chrome Framework -browser_thread_impl.cc:277 )	content::BrowserThreadImpl::IOThreadRun(base::RunLoop*)
0x000000010b061353	(Google Chrome Framework -browser_thread_impl.cc:312 )	content::BrowserThreadImpl::Run(base::RunLoop*)
0x000000010c5e2968	(Google Chrome Framework -thread.cc:333 )	base::Thread::ThreadMain()
0x000000010c5dda56	(Google Chrome Framework -platform_thread_posix.cc:71 )	base::(anonymous namespace)::ThreadFunc(void*)
0x00007fffa24daaaa	(libsystem_pthread.dylib + 0x00003aaa )	_pthread_body
0x00007fffa24da9f6	(libsystem_pthread.dylib + 0x000039f6 )	_pthread_start
0x00007fffa24da220	(libsystem_pthread.dylib + 0x00003220 )	thread_start
0x000000010c5dd9ff	(Google Chrome Framework + 0x01a219ff )	

Link to the list of the builds:
---------------------------------
https://crash.corp.google.com/browse?q=custom_data.ChromeCrashProto.magic_signature_1.name%3D%27midi%3A%3AMidiService%3A%3AEndSession%27&ignore_case=false&enable_rewrite=true&omit_field_name=&omit_field_value=&omit_field_opt=%3D

Bisect Information:
--------------------
Using the per-revision bisect providing the bisect results,

You are probably looking for a change made after 449578 (known good), but no later than 449579 (first known bad).

CHANGE-LOG URL:
---------------------------------------
https://chromium.googlesource.com/chromium/src/+log/7f190b5091427c5d08ad224415ff1b5e5f57b90f..f1860b973a77bc737dd64664cdc0e382cfbaccf0

From the CL above, assigning the issue to the concern owner
Review-Url: https://codereview.chromium.org/2672803002

perezju@ - Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Note: Since this is a regression issue marking it as RB-Dev please feel free to edit if this is not the case.

Thanks!

Issue 693023 has been merged into this issue.

My change is on test runners, nothing that gets compiled into Chrome, so pretty sure it can't be related to crashes reproduced manually.

Not exactly sure how this works, but the link above about the crash info points to:
r449574 Web MIDI: add dynamic MidiManager instantiation support for Linux

Which sounds like a lot more related to the stack above.

Just to update this seems to be specific to MIDI permission and Issue doesn't repro with other type of notifications on https://permission.site page. 

Link to the list of the OS where the crashes are seen:
=======================================================
https://crash.corp.google.com/browse?q=custom_data.ChromeCrashProto.magic_signature_1.name%3D%27midi%3A%3AMidiService%3A%3AEndSession%27&ignore_case=false&enable_rewrite=true&omit_field_name=&omit_field_value=&omit_field_opt=%3D

Single digits of crashes instances are seen on Windows,Mac and Linux and Android latest M-58(58.0.3014.0) shows 17 instances from 6 clients.

Not a Dev blocker since this is not a P0 functional use case.

Thank you!

Users experienced this crash on the following builds:

Mac Canary 58.0.3014.0 -  2.25 CPM, 3 reports, 3 clients (signature midi::MidiService::EndSession)

If this update was incorrect, please add "Fracas-Wrong" label to prevent future updates.

- Go/Fracas

A fix is already under code review.
Note: this is not a regression, but one newly added assertion finds a potential problem that does not matter actually now, but will be a problem for the new design.