Use multiple shared memory buffers cyclically for audio capture.

content/browser/renderer_host/media/audio_input_sync_writer.h

Index: content/browser/renderer_host/media/audio_input_sync_writer.h
===================================================================
--- content/browser/renderer_host/media/audio_input_sync_writer.h	(revision 186213)
+++ content/browser/renderer_host/media/audio_input_sync_writer.h	(working copy)
@@ -6,6 +6,7 @@
 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_INPUT_SYNC_WRITER_H_
 
 #include "base/file_descriptor_posix.h"
+#include "base/memory/scoped_vector.h"
 #include "base/process.h"
 #include "base/sync_socket.h"
 #include "media/audio/audio_input_controller.h"
@@ -21,8 +22,10 @@
 // process.
 class AudioInputSyncWriter : public media::AudioInputController::SyncWriter {
  public:
-  explicit AudioInputSyncWriter(base::SharedMemory* shared_memory);
+  typedef ScopedVector<base::SharedMemory> SharedMemoryVector;
 
+  explicit AudioInputSyncWriter(SharedMemoryVector* shared_memory);
+
   virtual ~AudioInputSyncWriter();
 
   // media::AudioOutputController::SyncWriter implementation.
@@ -39,7 +42,8 @@
 #endif
 
  private:
-  base::SharedMemory* shared_memory_;
+  SharedMemoryVector* shared_memory_;
+  size_t current_buffer_id_;
 
   // Socket for transmitting audio data.
   scoped_ptr<base::CancelableSyncSocket> socket_;