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

chrome/browser/sync_file_system/local/sync_file_system_backend.cc

Index: chrome/browser/sync_file_system/local/sync_file_system_backend.cc
diff --git a/chrome/browser/sync_file_system/local/sync_file_system_backend.cc b/chrome/browser/sync_file_system/local/sync_file_system_backend.cc
index c6b620cd06b7ee950a81600d0eb690c834de1fc3..3f630f7ef259a55076d59464af970ecd66ede6dc 100644
--- a/chrome/browser/sync_file_system/local/sync_file_system_backend.cc
+++ b/chrome/browser/sync_file_system/local/sync_file_system_backend.cc
@@ -4,6 +4,8 @@
 
 #include "chrome/browser/sync_file_system/local/sync_file_system_backend.h"
 
+#include <string>
+
 #include "base/logging.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/sync_file_system/local/local_file_change_tracker.h"
@@ -183,6 +185,7 @@ scoped_ptr<storage::FileStreamReader>
 SyncFileSystemBackend::CreateFileStreamReader(
     const storage::FileSystemURL& url,
     int64 offset,
+    int64 length,
     const base::Time& expected_modification_time,
     storage::FileSystemContext* context) const {
   DCHECK(CanHandleType(url.type()));