Convert some audio code to OnceCallback.

media/mojo/services/mojo_audio_output_stream_provider.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_MOJO_SERVICES_MOJO_AUDIO_OUTPUT_STREAM_PROVIDER_H_
 #define MEDIA_MOJO_SERVICES_MOJO_AUDIO_OUTPUT_STREAM_PROVIDER_H_
 
 #include <memory>
 #include <string>
 
 #include "base/threading/thread_checker.h"
 #include "media/audio/audio_output_delegate.h"
 #include "media/mojo/interfaces/audio_output_stream.mojom.h"
 #include "media/mojo/services/media_mojo_export.h"
 #include "media/mojo/services/mojo_audio_output_stream.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace media {
 
 // Provides a single AudioOutput, given the audio parameters to use.
 class MEDIA_MOJO_EXPORT MojoAudioOutputStreamProvider
     : NON_EXPORTED_BASE(public mojom::AudioOutputStreamProvider) {
  public:
   using CreateDelegateCallback =
       base::OnceCallback<std::unique_ptr<AudioOutputDelegate>(
           const AudioParameters& params,
           AudioOutputDelegate::EventHandler*)>;
-  using DeleterCallback = base::Callback<void(AudioOutputStreamProvider*)>;
+  using DeleterCallback = base::OnceCallback<void(AudioOutputStreamProvider*)>;
 
   // |create_delegate_callback| is used to obtain an AudioOutputDelegate for the
   // AudioOutput when it's initialized and |deleter_callback| is called when
   // this class should be removed (stream ended/error). |deleter_callback| is
   // required to destroy |this| synchronously.
   MojoAudioOutputStreamProvider(mojom::AudioOutputStreamProviderRequest request,
                                 CreateDelegateCallback create_delegate_callback,
                                 DeleterCallback deleter_callback);
 
   ~MojoAudioOutputStreamProvider() override;
 
  private:
   // mojom::AudioOutputStreamProvider implementation.
   void Acquire(mojom::AudioOutputStreamRequest stream_request,
                const AudioParameters& params,
                const AcquireCallback& acquire_callback) override;
 
+  // Called when |audio_output_| had an error.
+  void OnError();
+
   // The callback for the Acquire() must be stored until the response is ready.
   AcquireCallback acquire_callback_;
 
   base::Optional<MojoAudioOutputStream> audio_output_;
   mojo::Binding<AudioOutputStreamProvider> binding_;
   CreateDelegateCallback create_delegate_callback_;
-  base::Closure deleter_callback_;
+  DeleterCallback deleter_callback_;
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(MojoAudioOutputStreamProvider);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_MOJO_SERVICES_MOJO_AUDIO_OUTPUT_STREAM_PROVIDER_H_