Switch Speech Recognition to asynchronous callback-based AudioManager interactions.

media/audio/audio_system_impl.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 MEDIA_AUDIO_AUDIO_SYSTEM_IMPL_H_
+#define MEDIA_AUDIO_AUDIO_SYSTEM_IMPL_H_
+
+#include "media/audio/audio_system.h"
+
+namespace base {
+class SingleThreadTaskRunner;
+}
+
+namespace media {
+class AudioManager;
+
+class MEDIA_EXPORT AudioSystemImpl : public AudioSystem {
+ public:
+  static std::unique_ptr<AudioSystem> Create(AudioManager* audio_manager);
+
+  ~AudioSystemImpl() override;
+
+  // AudioSystem implementation.
+  void GetInputStreamParameters(
+      const std::string& device_id,
+      OnAudioParamsCallback on_params_cb) const override;
+  AudioManager* GetAudioManager() const override;
+
+ protected:
+  AudioSystemImpl(AudioManager* audio_manager);
+
+ private:
+  base::SingleThreadTaskRunner* GetTaskRunner() const;
+
+  AudioManager* const audio_manager_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioSystemImpl);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_AUDIO_AUDIO_SYSTEM_IMPL_H_