Use AudioUnit instead of AudioDevice properties to get channel count.

media/audio/BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/linux/pkg_config.gni")
 import("//media/media_options.gni")
 
 # When libpulse is not directly linked, use stubs to allow for dlopening of the
 # binary.
 if (!link_pulseaudio) {
@@ skipping 144 matching lines @@
       "mac/audio_auhal_mac.cc",
       "mac/audio_auhal_mac.h",
       "mac/audio_device_listener_mac.cc",
       "mac/audio_device_listener_mac.h",
       "mac/audio_input_mac.cc",
       "mac/audio_input_mac.h",
       "mac/audio_low_latency_input_mac.cc",
       "mac/audio_low_latency_input_mac.h",
       "mac/audio_manager_mac.cc",
       "mac/audio_manager_mac.h",
+      "mac/scoped_audio_unit.cc",
+      "mac/scoped_audio_unit.h",
     ]
     libs += [
       "AudioToolbox.framework",
       "AudioUnit.framework",
       "CoreAudio.framework",
     ]
   }
 
   if (is_win) {
     sources += [
@@ skipping 212 matching lines @@
     ]
   }
 
   if (use_alsa) {
     sources += [
       "alsa/alsa_output_unittest.cc",
       "audio_low_latency_input_output_unittest.cc",
     ]
   }
 }