Convert some audio code to OnceCallback.

content/browser/renderer_host/media/audio_output_authorization_handler.h

Index: content/browser/renderer_host/media/audio_output_authorization_handler.h
diff --git a/content/browser/renderer_host/media/audio_output_authorization_handler.h b/content/browser/renderer_host/media/audio_output_authorization_handler.h
index be56e14ccaf08e61771be7efd2728eef266d5c07..fb5d69c8d2929abc3b1f9091740ec7a9ca1078d9 100644
--- a/content/browser/renderer_host/media/audio_output_authorization_handler.h
+++ b/content/browser/renderer_host/media/audio_output_authorization_handler.h
@@ -36,12 +36,11 @@ class CONTENT_EXPORT AudioOutputAuthorizationHandler {
   // also has the default audio parameters for the device, and the id for the
   // device, which is needed to open a stream for the device. This id is not
   // hashed, so it must be hashed before sending it to the renderer.
-  // TODO(maxmorin): Change to OnceCallback once base:: code is ready for it.
   using AuthorizationCompletedCallback =
-      base::Callback<void(media::OutputDeviceStatus status,
-                          bool should_send_id,
-                          const media::AudioParameters& params,
-                          const std::string& raw_device_id)>;
+      base::OnceCallback<void(media::OutputDeviceStatus status,
+                              bool should_send_id,
+                              const media::AudioParameters& params,
+                              const std::string& raw_device_id)>;
 
   AudioOutputAuthorizationHandler(media::AudioSystem* audio_system,
                                   MediaStreamManager* media_stream_manager,