Change the way audio mixer gets "pending bytes" (amount of data currently buffered

media/audio/audio_output_mixer.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // AudioOutputMixer is a class that implements browser-side audio mixer.
 // AudioOutputMixer implements both AudioOutputDispatcher and
 // AudioSourceCallback interfaces.
 
 #ifndef MEDIA_AUDIO_AUDIO_OUTPUT_MIXER_H_
 #define MEDIA_AUDIO_AUDIO_OUTPUT_MIXER_H_
 
 #include <map>
+#include <set>
 
 #include "base/basictypes.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/synchronization/lock.h"
 #include "base/timer.h"
 #include "media/audio/audio_io.h"
 #include "media/audio/audio_manager.h"
 #include "media/audio/audio_output_dispatcher.h"
@@ skipping 31 matching lines @@
   virtual ~AudioOutputMixer();
 
   // Called by |close_timer_|. Closes physical stream.
   void ClosePhysicalStream();
 
   // The |lock_| must be acquired whenever we modify |proxies_| in the audio
   // manager thread or accessing it in the hardware audio thread. Read in the
   // audio manager thread is safe.
   base::Lock lock_;
 
+  // Information for each each in-flight buffer.
+  struct BufferData {
+    explicit BufferData(int len) : length(len) { }
+    int length;
+  };
+  typedef std::map<void*, BufferData> BufferMap;
+  BufferMap buffer_data_;
+
   // List of audio output proxies currently being played.
   // For every proxy we store aux structure containing data necessary for
   // mixing.
   struct ProxyData {
     AudioOutputStream::AudioSourceCallback* audio_source_callback;
     double volume;
     int pending_bytes;
+    std::set<void*> buffers;  // Used to catch when we stop prebuffering and
+                              // start releasing buffers.
+    bool prebuffering;
   };
   typedef std::map<AudioOutputProxy*, ProxyData> ProxyMap;
   ProxyMap proxies_;
 
   // Physical stream for this mixer.
   scoped_ptr<AudioOutputStream> physical_stream_;
 
   // Temporary buffer used when mixing. Allocated in the constructor
   // to avoid constant allocation/deallocation in the callback.
   scoped_array<uint8> mixer_data_;
 
   // Used to post delayed tasks to ourselves that we cancel inside Shutdown().
   base::WeakPtrFactory<AudioOutputMixer> weak_this_;
   base::DelayTimer<AudioOutputMixer> close_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioOutputMixer);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_OUTPUT_MIXER_H_