First step towards moving AudioDevice from content/ to media/audio.

media/audio/audio_output_ipc.h

Index: media/audio/audio_output_ipc.h
diff --git a/media/audio/audio_output_ipc.h b/media/audio/audio_output_ipc.h
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+// 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.
+
+#ifndef MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
+#define MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_
+
+#include "base/shared_memory.h"
+#include "base/sync_socket.h"
+#include "media/audio/audio_parameters.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+// Contains IPC notifications for the state of the server side
+// (AudioOutputController) audio state changes and when an AudioOutputController
+// has been created.  Implemented by AudioDevice.
+class MEDIA_EXPORT AudioOutputIPCDelegate {
+ public:
+  // Current status of the audio output stream in the browser process. Browser
+  // sends information about the current playback state and error to the
+  // renderer process using this type.
+  enum State {
+    kPlaying,
+    kPaused,
+    kError
+  };
+
+  // Called when state of an audio stream has changed.
+  virtual void OnStateChanged(State state) = 0;
+
+  // Called when an audio stream has been created.
+  // The shared memory |handle| points to a memory section that's used to
+  // transfer audio buffers from the AudioOutputIPCDelegate back to the
+  // AudioRendererHost.  The implementation of OnStreamCreated takes ownership.
+  // The |socket_handle| is used by AudioRendererHost to signal requests for
+  // audio data to be written into the shared memory. The AudioOutputIPCDelegate
+  // must read from this socket and provide audio whenever data (search for
+  // "pending_bytes") is received.
+  virtual void OnStreamCreated(base::SharedMemoryHandle handle,
+                               base::SyncSocket::Handle socket_handle,
+                               int length) = 0;
+
+  // Called when the AudioOutputIPC object is going away and/or when the IPC
+  // channel has been closed and no more ipc requests can be made.
+  // Implementations must clear any references to the AudioOutputIPC object
+  // at this point.
+  virtual void OnIPCClosed() = 0;
+
+ protected:
+  virtual ~AudioOutputIPCDelegate();
+};
+
+// Provides IPC functionality for an AudioDevice.  The implementation should
+// asynchronously deliver the messages to an AudioOutputController object (or
+// create one in the case of CreateStream()), that may live in a separate
+// process.
+class MEDIA_EXPORT AudioOutputIPC {
+ public:
+  // Registers an AudioOutputIPCDelegate and returns a |stream_id| that must
+  // be used with all other IPC functions in this interface.
+  virtual int AddDelegate(AudioOutputIPCDelegate* delegate) = 0;
+
+  // Unregisters a delegate that was previously registered via a call to
+  // AddDelegate().  The audio stream should be in a closed state prior to
+  // calling this function.
+  virtual void RemoveDelegate(int stream_id) = 0;
+
+  // Sends a request to create an AudioOutputController object in the peer
+  // process, identify it by |stream_id| and configure it to use the specified
+  // audio |params|.  Once the stream has been created, the implementation must
+  // generate a notification to the AudioOutputIPCDelegate and call
+  // OnStreamCreated().
+  virtual void CreateStream(int stream_id, const AudioParameters& params) = 0;
+
+  // Starts playing the stream.  This should generate a call to
+  // AudioOutputController::Play().
+  virtual void PlayStream(int stream_id) = 0;
+
+  // Pauses an audio stream.  This should generate a call to
+  // AudioOutputController::Pause().
+  virtual void PauseStream(int stream_id) = 0;
+
+  // "Flushes" the audio device. This should generate a call to
+  // AudioOutputController::Flush().
+  // TODO(tommi): This is currently neither implemented nor called.  Remove?
+  virtual void FlushStream(int stream_id) = 0;
+
+  // Closes the audio stream and deletes the matching AudioOutputController
+  // instance.  Prior to deleting the AudioOutputController object, a call to
+  // AudioOutputController::Close must be made.
+  virtual void CloseStream(int stream_id) = 0;
+
+  // Sets the volume of the audio stream.
+  virtual void SetVolume(int stream_id, double volume) = 0;
+
+ protected:
+  virtual ~AudioOutputIPC();
+};
+
+}  // namespace media
+
+#endif  // MEDIA_AUDIO_AUDIO_OUTPUT_IPC_H_