Add mojo interface for audio rendering.

content/browser/renderer_host/media/audio_output_impl.h

+// Copyright 2016 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_BROWSER_RENDERER_HOST_MEDIA_AUDIO_OUTPUT_IMPL_H_
+#define CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_OUTPUT_IMPL_H_
+
+#include <memory>
+#include <string>
+
+#include "base/single_thread_task_runner.h"
+#include "content/browser/renderer_host/media/audio_output_delegate.h"
+#include "content/common/content_export.h"
+#include "media/mojo/interfaces/audio_output.mojom.h"
+#include "mojo/public/cpp/bindings/binding.h"
+
+namespace content {
+
+class CONTENT_EXPORT AudioOutputImpl
+    : public media::mojom::AudioOutput,
+      public AudioOutputDelegate::EventHandler {

[o1ka, 2017/01/25 15:15:21]

Can we use aggregation instead of inheritance (wherever possible)?

+ public:
+  using DelegateFactoryCallback =

[o1ka, 2017/01/25 15:15:21]

CreateAudioOutputDelegateCallback maybe? Oe CreateDelegateCallback?
DelegateFactoryCallback sounds confusing to me, as if it's a callback to pass to
a delegate factory, and it's not clear what is produces.

+      base::OnceCallback<AudioOutputDelegate::UniquePtr(
+          AudioOutputDelegate::EventHandler*,
+          const media::AudioParameters&)>;
+
+  using FinishedCallback = base::OnceCallback<void(AudioOutputImpl*)>;

[o1ka, 2017/01/25 15:15:21]

What this name stands for?

+
+  AudioOutputImpl(media::mojom::AudioOutputRequest request,
+                  FinishedCallback finished_callback,
+                  DelegateFactoryCallback delegate_factory_callback);
+
+  ~AudioOutputImpl() override;
+
+  // media::mojom::AudioOutput implementation.
+  // May only be called via mojo, not directly.

[o1ka, 2017/01/25 15:15:21]

What does it mean?

+  void Start(const media::AudioParameters& params,
+             const StartCallback& callback) override;
+  void Play() override;
+  void Pause() override;
+  void SetVolume(double volume) override;
+
+  // AudioOutputDelegate::EventHandler implementation.
+  void OnStreamStateChanged(bool playing) override;
+  void OnStreamCreated(int stream_id,
+                       base::SharedMemory* shared_memory,
+                       base::CancelableSyncSocket* foreign_socket) override;
+  void OnStreamError(int stream_id) override;
+
+ private:
+  // Closes connection to client and notifies owner.
+  void OnError();
+
+  StartCallback start_callback_;
+  DelegateFactoryCallback delegate_factory_callback_;
+  FinishedCallback finished_callback_;
+  mojo::Binding<AudioOutput> binding_;
+  AudioOutputDelegate::UniquePtr delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioOutputImpl);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_AUDIO_OUTPUT_IMPL_H_