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

net/base/mock_file_stream.cc

Index: net/base/mock_file_stream.cc
diff --git a/net/base/mock_file_stream.cc b/net/base/mock_file_stream.cc
index 42c23cbe6b85e23aab965e3289723766d4fffc41..fccb7a0f079cb7137ed9c98e7aaa0bb8174e5878 100644
--- a/net/base/mock_file_stream.cc
+++ b/net/base/mock_file_stream.cc
@@ -54,8 +54,12 @@ int64 MockFileStream::Truncate(int64 bytes) {
   return ReturnError64(FileStream::Truncate(bytes));
 }
 
-int MockFileStream::Flush() {
-  return ReturnError(FileStream::Flush());
+int MockFileStream::Flush(const CompletionCallback& callback) {
+  return ReturnError(FileStream::Flush(callback));
+}
+
+int MockFileStream::FlushSync() {
+  return ReturnError(FileStream::FlushSync());
 }
 
 }  // namespace testing