=== Stock libpulse behaviour (NOFLIST=0, no LD_PRELOAD shim) ===
Second pa_operation_unref() trips libpulse's own refcount assertion
and SIGABRTs the unsandboxed audio-service utility process.

Assertion 'pa_atomic_load(&(o)->_ref) >= 1' failed at ../src/pulse/operation.c:68, function pa_operation_unref(). Aborting.

Symbolized SIGABRT stack (frames inside chrome):
  #8  libpulse.so  pa_operation_unref  (assertion: PA_REFCNT_VALUE(o) >= 1)
  #9  media/audio/pulse/pulse_util.cc:682           pa_operation_unref(op);   <-- redundant unref in MuteAllSinksExcept()
  #10 media/audio/pulse/pulse_loopback_manager.cc:100  pulse::MuteAllSinksExcept(...)
  #11 media/audio/pulse/audio_manager_pulse.cc:275     loopback_manager_->MakeLoopbackStream(...)
  #12 media/audio/pulse/audio_manager_pulse.cc:174     MakeLowLatencyInputStream
  #13 media/audio/audio_manager_base.cc                MakeAudioInputStream
  #14 services/audio/input_controller.cc:720           audio::InputController::DoCreate
  ...
  content/utility/utility_main.cc                      (--utility-sub-type=audio.mojom.AudioService --service-sandbox-type=none)