Add Mac OS X synchronized audio I/O back-end

media/base/audio_bus.cc

Index: media/base/audio_bus.cc
===================================================================
--- media/base/audio_bus.cc	(revision 156450)
+++ media/base/audio_bus.cc	(working copy)
@@ -10,6 +10,10 @@
 #include "media/audio/audio_parameters.h"
 #include "media/base/limits.h"
 
+#if defined(OS_MACOSX)
+#include <CoreAudio/CoreAudioTypes.h>
+#endif
+
 namespace media {
 
 static bool IsAligned(void* ptr) {
@@ -137,6 +141,28 @@
     DCHECK(IsAligned(channel_data_[i]));
 }
 
+#if defined(OS_MACOSX)
+AudioBus::AudioBus(int channels, int frames, AudioBufferList* buffer_list)
+    : frames_(frames) {
+  ValidateConfig(channels, frames_);
+
+  channel_data_.reserve(channels);
+
+  // Copy pointers from AudioBufferList.
+  // It's ok to pass in a |buffer_list| with fewer channels, in which
+  // case we just duplicate the last channel.
+  int source_idx = 0;
+  for (int i = 0; i < channels; ++i) {
+    channel_data_.push_back(
+        static_cast<float*>(buffer_list->mBuffers[source_idx].mData));
+    DCHECK(IsAligned(channel_data_[i]));
+
+    if (source_idx < channels - 1)
+      ++source_idx;
+  }
+}
+#endif
+
 AudioBus::~AudioBus() {}
 
 scoped_ptr<AudioBus> AudioBus::Create(int channels, int frames) {