Convert some audio code to OnceCallback.

media/audio/audio_system.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_H_
 #define MEDIA_AUDIO_AUDIO_SYSTEM_H_
 
+#include <string>
+
 #include "base/callback.h"
 #include "media/audio/audio_device_description.h"
 #include "media/base/audio_parameters.h"
 #include "media/base/media_export.h"
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace media {
 class AudioManager;
 
 // Work in progress: Provides asynchronous interface to AudioManager. All the
 // AudioManager clients will be switched to it, in preparation for moving
 // to Mojo audio service.
 class MEDIA_EXPORT AudioSystem {
  public:
   // Replies are asynchronously sent from audio system thread to the thread the
   // call is issued on. Attention! Audio system thread may outlive the client
   // objects; bind callbacks with care.
-  using OnAudioParamsCallback = base::Callback<void(const AudioParameters&)>;
-  using OnBoolCallback = base::Callback<void(bool)>;
+  using OnAudioParamsCallback =
+      base::OnceCallback<void(const AudioParameters&)>;
+  using OnBoolCallback = base::OnceCallback<void(bool)>;
   using OnDeviceDescriptionsCallback =
-      base::Callback<void(AudioDeviceDescriptions)>;
-  using OnDeviceIdCallback = base::Callback<void(const std::string&)>;
-  using OnInputDeviceInfoCallback = base::Callback<
+      base::OnceCallback<void(AudioDeviceDescriptions)>;
+  using OnDeviceIdCallback = base::OnceCallback<void(const std::string&)>;
+  using OnInputDeviceInfoCallback = base::OnceCallback<
       void(const AudioParameters&, const AudioParameters&, const std::string&)>;
 
   // Must not be called on audio system thread if it differs from the one
   // AudioSystem is destroyed on. See http://crbug.com/705455.
   static AudioSystem* Get();
 
   virtual ~AudioSystem();
 
   // Callback may receive invalid parameters, it means the specified device is
   // not found. This is best-effort: valid parameters do not guarantee existance
@@ skipping 43 matching lines @@
   // Sets the global AudioSystem pointer to the specified non-null value.
   static void SetInstance(AudioSystem* audio_system);
 
   // Sets the global AudioSystem pointer to null if it equals the specified one.
   static void ClearInstance(const AudioSystem* audio_system);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_AUDIO_AUDIO_SYSTEM_H_