[fsp] Improve performance for reading small chunks of data.

storage/browser/fileapi/file_system_context.h

 // Copyright (c) 2012 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 STORAGE_BROWSER_FILEAPI_FILE_SYSTEM_CONTEXT_H_
 #define STORAGE_BROWSER_FILEAPI_FILE_SYSTEM_CONTEXT_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 234 matching lines @@
   // Creates new FileStreamReader instance to read a file pointed by the given
   // filesystem URL |url| starting from |offset|. |expected_modification_time|
   // specifies the expected last modification if the value is non-null, the
   // reader will check the underlying file's actual modification time to see if
   // the file has been modified, and if it does any succeeding read operations
   // should fail with ERR_UPLOAD_FILE_CHANGED error.
   // This method internally cracks the |url|, get an appropriate
   // FileSystemBackend for the URL and call the backend's CreateFileReader.
   // The resolved FileSystemBackend could perform further specialization
   // depending on the filesystem type pointed by the |url|.
+  // At most |max_bytes_to_read| can be fetched from the file stream reader.
   scoped_ptr<storage::FileStreamReader> CreateFileStreamReader(
       const FileSystemURL& url,
       int64 offset,
+      int64 max_bytes_to_read,
       const base::Time& expected_modification_time);
 
   // Creates new FileStreamWriter instance to write into a file pointed by
   // |url| from |offset|.
   scoped_ptr<FileStreamWriter> CreateFileStreamWriter(
       const FileSystemURL& url,
       int64 offset);
 
   // Creates a new FileSystemOperationRunner.
   scoped_ptr<FileSystemOperationRunner> CreateFileSystemOperationRunner();
@@ skipping 151 matching lines @@
 
 struct DefaultContextDeleter {
   static void Destruct(const FileSystemContext* context) {
     context->DeleteOnCorrectThread();
   }
 };
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_FILEAPI_FILE_SYSTEM_CONTEXT_H_