MTP Streaming: Optimize block reading

chrome/browser/media_galleries/fileapi/mtp_device_async_delegate.h

 // Copyright (c) 2013 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_MTP_DEVICE_ASYNC_DELEGATE_H_
 #define CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_MTP_DEVICE_ASYNC_DELEGATE_H_
 
 #include "base/callback.h"
 #include "base/files/file.h"
 #include "base/memory/ref_counted.h"
@@ skipping 26 matching lines @@
   // A callback to be called when GetFileInfo/ReadDirectory/CreateSnapshot
   // method call fails.
   typedef base::Callback<void(base::File::Error error)> ErrorCallback;
 
   // A callback to be called when CreateSnapshotFile method call succeeds.
   typedef base::Callback<
       void(const base::File::Info& file_info,
            const base::FilePath& local_path)> CreateSnapshotFileSuccessCallback;
 
   // A callback to be called when ReadBytes method call succeeds.
-  typedef base::Callback<void(int)> ReadBytesSuccessCallback;
+  typedef base::Callback<
+      void(const base::File::Info& file_info,
+           int bytes_read)> ReadBytesSuccessCallback;
 
   struct ReadBytesRequest {
     ReadBytesRequest(const std::string& device_file_relative_path,
                      net::IOBuffer* buf, int64 offset, int buf_len,
                      const ReadBytesSuccessCallback& success_callback,
                      const ErrorCallback& error_callback);
     ~ReadBytesRequest();
 
     std::string device_file_relative_path;
     scoped_refptr<net::IOBuffer> buf;
@@ skipping 54 matching lines @@
 };
 
 typedef base::Callback<void(MTPDeviceAsyncDelegate*)>
     CreateMTPDeviceAsyncDelegateCallback;
 
 void CreateMTPDeviceAsyncDelegate(
     const base::FilePath::StringType& device_location,
     const CreateMTPDeviceAsyncDelegateCallback& callback);
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_MTP_DEVICE_ASYNC_DELEGATE_H_