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

storage/browser/fileapi/file_system_context.h

Index: storage/browser/fileapi/file_system_context.h
diff --git a/storage/browser/fileapi/file_system_context.h b/storage/browser/fileapi/file_system_context.h
index 09b2409acab8b189508a832d1c97bab9c18f0dbd..ca982719c292adec083a0b2b3443353fc287f5c1 100644
--- a/storage/browser/fileapi/file_system_context.h
+++ b/storage/browser/fileapi/file_system_context.h
@@ -252,9 +252,11 @@ class STORAGE_EXPORT FileSystemContext
   // 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