Use preferred channel layout on macOS instead of total channel count.

media/base/channel_layout.cc

Index: media/base/channel_layout.cc
diff --git a/media/base/channel_layout.cc b/media/base/channel_layout.cc
index 9d85842e749117ce96440a8d14d0d5c484840851..7d3e754df187f01a67227d54d2ace500dc8f6e0a 100644
--- a/media/base/channel_layout.cc
+++ b/media/base/channel_layout.cc
@@ -160,6 +160,7 @@ static const int kChannelOrderings[CHANNEL_LAYOUT_MAX + 1][CHANNELS_MAX + 1] = {
 
 int ChannelLayoutToChannelCount(ChannelLayout layout) {
   DCHECK_LT(static_cast<size_t>(layout), arraysize(kLayoutToChannels));
+  DCHECK_LE(kLayoutToChannels[layout], kMaxConcurrentChannels);
   return kLayoutToChannels[layout];
 }