Use OnceCallback on Mojo interfaces in //chrome/common/extensions

chrome/browser/media_galleries/fileapi/safe_media_metadata_parser.h

 // Copyright 2014 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 CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_SAFE_MEDIA_METADATA_PARSER_H_
 #define CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_SAFE_MEDIA_METADATA_PARSER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 53 matching lines @@
   // Callback from utility process when it finishes parsing metadata.
   // Runs on the IO thread.
   void ParseMediaMetadataDone(
       bool parse_success,
       std::unique_ptr<base::DictionaryValue> metadata_dictionary,
       const std::vector<AttachedImage>& attached_images);
 
   // Sequence of functions that bounces from the IO thread to the UI thread to
   // read the blob data, then sends the data back to the utility process.
   void StartBlobRequest(
-      const extensions::mojom::MediaDataSource::ReadBlobCallback& callback,
+      extensions::mojom::MediaDataSource::ReadBlobCallback callback,
       int64_t position,
       int64_t length);
   void StartBlobReaderOnUIThread(
-      const extensions::mojom::MediaDataSource::ReadBlobCallback& callback,
+      extensions::mojom::MediaDataSource::ReadBlobCallback callback,
       int64_t position,
       int64_t length);
   void BlobReaderDoneOnUIThread(
-      const extensions::mojom::MediaDataSource::ReadBlobCallback& callback,
+      extensions::mojom::MediaDataSource::ReadBlobCallback callback,
       std::unique_ptr<std::string> data,
       int64_t /* blob_total_size */);
   void FinishBlobRequest(
-      const extensions::mojom::MediaDataSource::ReadBlobCallback& callback,
+      extensions::mojom::MediaDataSource::ReadBlobCallback callback,
       std::unique_ptr<std::string> data);
 
   // All member variables are only accessed on the IO thread.
   Profile* const profile_;
   const std::string blob_uuid_;
   const int64_t blob_size_;
   const std::string mime_type_;
   bool get_attached_images_;
 
   DoneCallback callback_;
 
   std::unique_ptr<
       content::UtilityProcessMojoClient<extensions::mojom::MediaParser>>
       utility_process_mojo_client_;
 
   std::unique_ptr<MediaDataSourceImpl> media_data_source_;
 
   DISALLOW_COPY_AND_ASSIGN(SafeMediaMetadataParser);
 };
 
 }  // namespace metadata
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_SAFE_MEDIA_METADATA_PARSER_H_