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

webkit/browser/fileapi/file_system_context.h

Index: webkit/browser/fileapi/file_system_context.h
diff --git a/webkit/browser/fileapi/file_system_context.h b/webkit/browser/fileapi/file_system_context.h
index cbebf030faed564fdd4a773bc0a7355641eb3337..33fa8dc082642b5392fc5bbf3f8cd529aebe835e 100644
--- a/webkit/browser/fileapi/file_system_context.h
+++ b/webkit/browser/fileapi/file_system_context.h
@@ -251,9 +251,11 @@ 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 |limit| bytes can be fetched from the file stream reader.
   scoped_ptr<storage::FileStreamReader> CreateFileStreamReader(
       const FileSystemURL& url,
       int64 offset,
+      int64 limit,
       const base::Time& expected_modification_time);
 
   // Creates new FileStreamWriter instance to write into a file pointed by