Introduce AudioIPCFactory.

content/renderer/media/audio_ipc_factory.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_AUDIO_IPC_FACTORY_H_
+#define CONTENT_RENDERER_MEDIA_AUDIO_IPC_FACTORY_H_
+
+#include <memory>
+
+#include "base/containers/flat_map.h"
+#include "base/memory/ref_counted.h"
+#include "content/common/content_export.h"
+#include "content/common/media/renderer_audio_output_stream_factory.mojom.h"
+#include "content/renderer/media/audio_message_filter.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace media {
+class AudioOutputIPC;
+}
+
+namespace service_manager {
+class InterfaceProvider;
+}
+
+namespace content {
+
+// This is a factory for AudioOutputIPC objects. It has two modes, using either
+// AudioMessageFilter or Mojo RendererAudioOutputStreamFactory objects. It is
+// threadsafe. This class is designed to be leaked at shutdown, as it posts
+// tasks to itself using base::Unretained and also hands out references to
+// itself in the AudioOutputIPCs it creates, but in the case where the owner is
+// sure that there are no outstanding references (such as in a unit test), the
+// class can be destructed.
+// TODO(maxmorin): Registering the factories for each frame will become
+// unnecessary when crbug.com/668275 is fixed. When that is done, this class can
+// be greatly simplified.
+class CONTENT_EXPORT AudioIPCFactory {
+ public:
+  AudioIPCFactory(
+      const scoped_refptr<AudioMessageFilter>& audio_message_filter,

[DaleCurtis, 2017/05/31 20:48:09]

No const&.

[Max Morin, 2017/06/01 13:58:43]

Done.

+      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
+  ~AudioIPCFactory();
+
+  static AudioIPCFactory* get() { return instance_; }
+
+  const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner() const {

[DaleCurtis, 2017/05/31 20:48:09]

Ditto.

[Max Morin, 2017/06/01 13:58:43]

Done.

+    return io_task_runner_;
+  }
+
+  // Enables |this| to create MojoAudioOutputIPCs for the specified frame.

[DaleCurtis, 2017/05/31 20:48:09]

Comment needs to qualify why this is labeled Maybe.

[Max Morin, 2017/06/01 13:58:43]

Done.

+  void MaybeRegisterRemoteFactory(
+      int frame_id,
+      service_manager::InterfaceProvider* interface_provider);
+
+  // Every call to the above method must be matched by a call to this one when

[DaleCurtis, 2017/05/31 20:48:09]

Ditto.

[Max Morin, 2017/06/01 13:58:43]

Done.

+  // the frame is destroyed.
+  void MaybeDeregisterRemoteFactory(int frame_id);
+
+  // The returned object may only be used on |io_task_runner()|.
+  std::unique_ptr<media::AudioOutputIPC> CreateAudioOutputIPC(
+      int frame_id) const;
+
+ private:
+  using StreamFactoryMap =
+      base::flat_map<int, mojom::RendererAudioOutputStreamFactoryPtr>;
+
+  mojom::RendererAudioOutputStreamFactory* GetRemoteFactory(int frame_id) const;
+
+  void RegisterRemoteFactoryOnIOThread(
+      int frame_id,
+      mojom::RendererAudioOutputStreamFactoryPtrInfo factory_ptr_info);
+
+  // Indicates whether mojo factories are used.
+  bool UsingMojoFactories() const;
+
+  // Maps frame id to the corresponding factory.
+  StreamFactoryMap factory_ptrs_;
+
+  // If this is non-null, it will be used rather than using mojo implementation.
+  const scoped_refptr<AudioMessageFilter> audio_message_filter_;
+
+  const scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+
+  // Global instance, set in constructor and unset in destructor.
+  static AudioIPCFactory* instance_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioIPCFactory);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_RENDERER_MEDIA_AUDIO_IPC_FACTORY_H_