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

content/browser/fileapi/upload_file_system_file_element_reader.cc

Index: content/browser/fileapi/upload_file_system_file_element_reader.cc
diff --git a/content/browser/fileapi/upload_file_system_file_element_reader.cc b/content/browser/fileapi/upload_file_system_file_element_reader.cc
index 0cbc668f2006ad5128d1c12f62b53efa03a4e305..6ccadf7e12da18ba840d76b6b7f0085311aecde9 100644
--- a/content/browser/fileapi/upload_file_system_file_element_reader.cc
+++ b/content/browser/fileapi/upload_file_system_file_element_reader.cc
@@ -7,6 +7,7 @@
 #include <algorithm>
 
 #include "base/bind.h"
+#include "base/numerics/safe_conversions.h"
 #include "net/base/net_errors.h"
 #include "webkit/browser/blob/file_stream_reader.h"
 #include "webkit/browser/fileapi/file_system_context.h"
@@ -41,11 +42,11 @@ int UploadFileSystemFileElementReader::Init(
   position_ = 0;
 
   // Initialize the stream reader and the length.
-  stream_reader_ =
-      file_system_context_->CreateFileStreamReader(
-          file_system_context_->CrackURL(url_),
-          range_offset_,
-          expected_modification_time_);
+  stream_reader_ = file_system_context_->CreateFileStreamReader(
+      file_system_context_->CrackURL(url_),
+      range_offset_,
+      base::checked_cast<int64>(range_length_),
+      expected_modification_time_);
   DCHECK(stream_reader_);
 
   const int64 result = stream_reader_->GetLength(