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 157152)
+++ media/base/audio_bus.cc	(working copy)
@@ -137,6 +137,13 @@
     DCHECK(IsAligned(channel_data_[i]));
 }
 
+AudioBus::AudioBus(int channels)
+    : channel_data_(channels),
+      frames_(0) {
+  for (size_t i = 0; i < channel_data_.size(); ++i)
+    channel_data_[i] = NULL;
+}
+
 AudioBus::~AudioBus() {}
 
 scoped_ptr<AudioBus> AudioBus::Create(int channels, int frames) {
@@ -148,6 +155,10 @@
       params.channels(), params.frames_per_buffer()));
 }
 
+scoped_ptr<AudioBus> AudioBus::Create(int channels) {
+  return scoped_ptr<AudioBus>(new AudioBus(channels));
+}
+
 scoped_ptr<AudioBus> AudioBus::WrapVector(
     int frames, const std::vector<float*>& channel_data) {
   return scoped_ptr<AudioBus>(new AudioBus(frames, channel_data));
@@ -170,6 +181,13 @@
       static_cast<float*>(data)));
 }
 
+void AudioBus::SetChannelData(int channel, float* data) {

[DaleCurtis, 2012/09/17 21:17:36]

This can lead to some pretty confusing situations:
1. WrapMemory(<some contiguous block>)
2. SetChannelData(0, <some channel data>)

Now the wrapped bus isn't writing all of its data to the wrapped memory region.

Maybe we should prevent usage of this method with WrapMemory and WrapVector
objects? If so the constructor above should set <some flag> and
DCHECK(data_.get() || <some flag>);

[Chris Rogers, 2012/09/17 22:00:42]

We can discuss offline...

+  CHECK_GE(channel, 0);
+  CHECK_LT(static_cast<size_t>(channel), channel_data_.size());
+  DCHECK(IsAligned(data));
+  channel_data_[channel] = data;
+}
+
 void AudioBus::ZeroFramesPartial(int start_frame, int frames) {
   CheckOverflow(start_frame, frames, frames_);