Flush at the end of local file writing in FileWriter API.

net/base/file_stream.cc

Index: net/base/file_stream.cc
diff --git a/net/base/file_stream.cc b/net/base/file_stream.cc
index 1707fb755ec140ea653c42eff11ebe4834a95529..df18ad098b3a8318dac45624ae7ab328d5624527 100644
--- a/net/base/file_stream.cc
+++ b/net/base/file_stream.cc
@@ -78,8 +78,12 @@ int64 FileStream::Truncate(int64 bytes) {
   return impl_.Truncate(bytes);
 }
 
-int FileStream::Flush() {
-  return impl_.Flush();
+int FileStream::Flush(const CompletionCallback& callback) {
+  return impl_.Flush(callback);
+}
+
+int FileStream::FlushSync() {
+  return impl_.FlushSync();
 }
 
 void FileStream::EnableErrorStatistics() {