Use multiple shared memory buffers cyclically for audio capture.

media/audio/audio_input_ipc.h

Index: media/audio/audio_input_ipc.h
===================================================================
--- media/audio/audio_input_ipc.h	(revision 186213)
+++ media/audio/audio_input_ipc.h	(working copy)
@@ -25,17 +25,24 @@
   };
 
   // Called when an AudioInputController has been created.
-  // The shared memory |handle| points to a memory section that's used to
-  // transfer data between the AudioInputDevice and AudioInputController
-  // objects.  The implementation of OnStreamCreated takes ownership.
   // The |socket_handle| is used by the AudioInputController to signal
   // notifications that more data is available and can optionally provide
-  // parameter changes back.  The AudioInputDevice must read from this socket
+  // parameter changes back. The AudioInputDevice must read from this socket
   // and process the shared memory whenever data is read from the socket.
-  virtual void OnStreamCreated(base::SharedMemoryHandle handle,
-                               base::SyncSocket::Handle socket_handle,
-                               int length) = 0;
+  // The |total_handles| states how many shared memory buffers are used to
+  // transfer data.
+  virtual void OnStreamCreated(base::SyncSocket::Handle socket_handle,
+                               int total_handles) = 0;
 
+  // Called when an AudioInputController has been created.
+  // The shared memory |handle| points to a memory section that's used to
+  // transfer data between the AudioInputDevice and AudioInputController
+  // objects. The implementation of OnStreamCreated takes ownership.
+  // The memory has |length| size and its id is |index|.
+  virtual void OnSharedMemoryCreated(base::SharedMemoryHandle handle,
+                                     int length,
+                                     int index) = 0;
+
   // Called when state of an audio stream has changed.
   virtual void OnStateChanged(State state) = 0;
 
@@ -76,8 +83,12 @@
   // audio |params|.  Once the stream has been created, the implementation must
   // generate a notification to the AudioInputIPCDelegate and call
   // OnStreamCreated().
-  virtual void CreateStream(int stream_id, const AudioParameters& params,
-      const std::string& device_id, bool automatic_gain_control) = 0;
+  virtual void CreateStream(
+      int stream_id,
+      const AudioParameters& params,
+      const std::string& device_id,
+      bool automatic_gain_control,
+      int shared_memory_count) = 0;
 
   // Starts the device on the server side.  Once the device has started,
   // or failed to start, a callback to