Add a mojo implementation of AudioOutputIPC.

content/renderer/media/mojo_audio_output_ipc.h

+// Copyright 2017 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 CONTENT_RENDERER_MEDIA_MOJO_AUDIO_OUTPUT_IPC_H_
+#define CONTENT_RENDERER_MEDIA_MOJO_AUDIO_OUTPUT_IPC_H_
+
+#include <string>
+
+#include "base/macros.h"
+#include "base/memory/weak_ptr.h"
+#include "base/threading/thread_checker.h"
+#include "content/common/media/renderer_audio_output_stream_factory.mojom.h"
+#include "media/audio/audio_output_ipc.h"
+
+namespace content {
+
+// MojoAudioOutputIPC is a renderer-side class for handling creation,
+// initialization and control of an output stream.

[o1ka, 2017/04/20 10:36:00]

Could you add a comment on threading (it can run on IO thread only, the
limitation comes from AudioIPCFactory::GetRemoteFactory() )?
(and maybe in media::AudioOutputIPC as well)

[Max Morin, 2017/05/05 13:10:59]

In the current version, it may only be used on a single thread. (In practice
this is the io thread since the factory accessor may only be called from the io
thread, but this not really a property of this class).

+class MojoAudioOutputIPC : public media::AudioOutputIPC {
+ public:
+  explicit MojoAudioOutputIPC(int frame_id);
+
+  ~MojoAudioOutputIPC() override;
+
+  // AudioOutputIPC implementation.
+  void RequestDeviceAuthorization(media::AudioOutputIPCDelegate* delegate,
+                                  int session_id,
+                                  const std::string& device_id,
+                                  const url::Origin& security_origin) override;
+  void CreateStream(media::AudioOutputIPCDelegate* delegate,
+                    const media::AudioParameters& params) override;
+  void PlayStream() override;
+  void PauseStream() override;
+  void CloseStream() override;
+  void SetVolume(double volume) override;
+
+ private:
+  media::mojom::AudioOutputStreamProviderRequest MakeProviderRequest(
+      media::AudioOutputIPCDelegate* delegate);
+
+  void RecievedDeviceAuthorization(media::AudioOutputIPCDelegate* delegate,
+                                   media::OutputDeviceStatus status,
+                                   const media::AudioParameters& params,
+                                   const std::string& device_id) const;
+
+  void StreamCreated(media::AudioOutputIPCDelegate* delegate,
+                     mojo::ScopedSharedBufferHandle shared_memory,
+                     mojo::ScopedHandle socket);
+
+  base::ThreadChecker thread_checker_;

[o1ka, 2017/04/20 10:36:00]

it can run on AudioIPCFactory::io_task_runner only, right?

[Max Morin, 2017/05/05 13:10:59]

See above.

+  const int frame_id_;
+
+  media::mojom::AudioOutputStreamProviderPtr stream_provider_;
+  media::mojom::AudioOutputStreamPtr stream_;
+
+  // To make sure we don't send an "authorization completed" callback for a
+  // stream after it's closed, we use this weak factory.
+  base::WeakPtrFactory<MojoAudioOutputIPC> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(MojoAudioOutputIPC);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_MOJO_AUDIO_OUTPUT_IPC_H_