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

media/audio/mac/audio_manager_mac.cc

Index: media/audio/mac/audio_manager_mac.cc
===================================================================
--- media/audio/mac/audio_manager_mac.cc	(revision 156450)
+++ media/audio/mac/audio_manager_mac.cc	(working copy)
@@ -6,6 +6,7 @@
 
 #include <string>
 
+#include "base/command_line.h"
 #include "base/mac/mac_logging.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/sys_string_conversions.h"
@@ -14,7 +15,9 @@
 #include "media/audio/mac/audio_low_latency_output_mac.h"
 #include "media/audio/mac/audio_manager_mac.h"
 #include "media/audio/mac/audio_output_mac.h"
+#include "media/audio/mac/audio_synchronized_mac.h"
 #include "media/base/limits.h"
+#include "media/base/media_switches.h"
 
 namespace media {
 
@@ -250,7 +253,18 @@
 AudioOutputStream* AudioManagerMac::MakeLowLatencyOutputStream(
     const AudioParameters& params) {
   DCHECK_EQ(AudioParameters::AUDIO_PCM_LOW_LATENCY, params.format());
-  return new AUAudioOutputStream(this, params);
+
+  // TODO(crogers): remove once we properly handle input device selection.
+  if (CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableWebAudioInput)) {
+    // kAudioDeviceUnknown translates to "use default" here.
+    return new AudioSynchronizedStream(this,
+                                       params,
+                                       kAudioDeviceUnknown,
+                                       kAudioDeviceUnknown);
+  } else {
+    return new AUAudioOutputStream(this, params);
+  }
 }
 
 AudioInputStream* AudioManagerMac::MakeLinearInputStream(