Audio software mixer.

media/audio/audio_manager_base.cc

Index: media/audio/audio_manager_base.cc
===================================================================
--- media/audio/audio_manager_base.cc	(revision 132979)
+++ media/audio/audio_manager_base.cc	(working copy)
@@ -5,12 +5,15 @@
 #include "media/audio/audio_manager_base.h"
 
 #include "base/bind.h"
+#include "base/command_line.h"
 #include "base/message_loop_proxy.h"
 #include "base/threading/thread.h"
-#include "media/audio/audio_output_dispatcher.h"
+#include "media/audio/audio_output_dispatcher_impl.h"
+#include "media/audio/audio_output_mixer.h"
 #include "media/audio/audio_output_proxy.h"
 #include "media/audio/fake_audio_input_stream.h"
 #include "media/audio/fake_audio_output_stream.h"
+#include "media/base/media_switches.h"
 
 namespace media {
 
@@ -136,9 +139,16 @@
 
   scoped_refptr<AudioOutputDispatcher>& dispatcher =
       output_dispatchers_[params];
-  if (!dispatcher)
-    dispatcher = new AudioOutputDispatcher(
-        this, params, base::TimeDelta::FromSeconds(kStreamCloseDelaySeconds));
+  if (!dispatcher) {
+    base::TimeDelta close_delay =
+        base::TimeDelta::FromSeconds(kStreamCloseDelaySeconds);
+    const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+    if (cmd_line->HasSwitch(switches::kEnableAudioMixer)) {
+      dispatcher = new AudioOutputMixer(this, params, close_delay);
+    } else {
+      dispatcher = new AudioOutputDispatcherImpl(this, params, close_delay);
+    }
+  }
   return new AudioOutputProxy(dispatcher);
 }