Audio software mixer.

media/audio/audio_output_proxy.h

Index: media/audio/audio_output_proxy.h
===================================================================
--- media/audio/audio_output_proxy.h	(revision 128216)
+++ media/audio/audio_output_proxy.h	(working copy)
@@ -8,6 +8,7 @@
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
 #include "base/threading/non_thread_safe.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_parameters.h"
@@ -29,6 +30,19 @@
   // Caller keeps ownership of |dispatcher|.
   explicit AudioOutputProxy(AudioOutputDispatcher* dispatcher);
 
+  // Accessors.
+  AudioSourceCallback* audio_source_callback() const {
+    return audio_source_callback_;
+  }
+
+  int pending_bytes() const {
+    return pending_bytes_;
+  }
+
+  void set_pending_bytes(int pending_bytes) {
+    pending_bytes_ = pending_bytes;
+  }
+
   // AudioOutputStream interface.
   virtual bool Open() OVERRIDE;
   virtual void Start(AudioSourceCallback* callback) OVERRIDE;
@@ -59,6 +73,16 @@
   // is stopped, and then started again.
   double volume_;
 
+  // Callback.
+  AudioSourceCallback* audio_source_callback_;
+
+  // Lock protecting |volume_| -- we can read it in the hardware audio thread.
+  base::Lock lock_;
+
+  // Number of pending bytes in the buffer.
+  // Initialized in Start() and after that accessed only in the hardware thread.
+  int pending_bytes_;
+
   DISALLOW_COPY_AND_ASSIGN(AudioOutputProxy);
 };