Fix zero channel count being returned for unknown macOS layouts.

media/audio/mac/audio_manager_mac.cc

 // Copyright (c) 2012 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.
 
 #include "media/audio/mac/audio_manager_mac.h"
 
 #include <algorithm>
 #include <limits>
 #include <vector>
 
@@ skipping 429 matching lines @@
                                         AudioObjectPropertyScope scope,
                                         int* channels) {
   DCHECK(AudioManager::Get()->GetTaskRunner()->BelongsToCurrentThread());
   CHECK(channels);
 
   // If the device has more channels than possible for layouts to express, use
   // the total count of channels on the device; as of this writing, macOS will
   // only return up to 8 channels in any layout. To allow WebAudio to work with
   // > 8 channel devices, we must use the total channel count instead of the
   // channel count of the preferred layout.
-  if (GetDeviceTotalChannelCount(device, scope, channels) &&
-      *channels > kMaxConcurrentChannels) {
+  int total_channel_count = 0;
+  if (GetDeviceTotalChannelCount(device, scope, &total_channel_count) &&
+      total_channel_count > kMaxConcurrentChannels) {
+    *channels = total_channel_count;
     return true;
   }
 
   AudioObjectPropertyAddress pa = {kAudioDevicePropertyPreferredChannelLayout,
                                    scope, kAudioObjectPropertyElementMaster};
   UInt32 size;
   OSStatus result = AudioObjectGetPropertyDataSize(device, &pa, 0, 0, &size);
   if (result != noErr || !size)
     return false;
 
@@ skipping 41 matching lines @@
     *channels = layout->mNumberChannelDescriptions;
   } else {
     *channels = 0;
     for (UInt32 i = 0; i < layout->mNumberChannelDescriptions; ++i) {
       if (layout->mChannelDescriptions[i].mChannelLabel !=
           kAudioChannelLabel_Unknown)
         (*channels)++;
     }
   }
 
+  // If we still don't have a channel count, fall back to total channel count.
+  if (*channels == 0) {
+    DLOG(WARNING) << "Unable to use channel layout for channel count.";
+    *channels = total_channel_count;
+  }
+
   DVLOG(1) << (scope == kAudioDevicePropertyScopeInput ? "Input" : "Output")
            << " channels: " << *channels;
   return true;
 }
 
 // static
 int AudioManagerMac::HardwareSampleRateForDevice(AudioDeviceID device_id) {
   DCHECK(AudioManager::Get()->GetTaskRunner()->BelongsToCurrentThread());
   Float64 nominal_sample_rate;
   UInt32 info_size = sizeof(nominal_sample_rate);
@@ skipping 637 matching lines @@
 ScopedAudioManagerPtr CreateAudioManager(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
     AudioLogFactory* audio_log_factory) {
   return ScopedAudioManagerPtr(
       new AudioManagerMac(std::move(task_runner), std::move(worker_task_runner),
                           audio_log_factory));
 }
 
 }  // namespace media