drive: Do not clear dirty bit if someone is writing to the file

chrome/browser/chromeos/drive/file_system/update_operation.cc

Index: chrome/browser/chromeos/drive/file_system/update_operation.cc
diff --git a/chrome/browser/chromeos/drive/file_system/update_operation.cc b/chrome/browser/chromeos/drive/file_system/update_operation.cc
index b9932c6b41341a21967f76e76c5723c3023bb4dc..6ce958f65faa26f6c540d753ecb54ab3745f2918 100644
--- a/chrome/browser/chromeos/drive/file_system/update_operation.cc
+++ b/chrome/browser/chromeos/drive/file_system/update_operation.cc
@@ -95,7 +95,9 @@ FileError UpdateFileLocalState(
   if (drive_file_path->empty())
     return FILE_ERROR_NOT_FOUND;
 
-  // Clear the dirty bit if we have updated an existing file.
+  // Do not clear the dirty bit if someone is writing to the file.
+  if (cache->IsOpenedForWrite(local_id))
+    return FILE_ERROR_OK;
   return cache->ClearDirty(local_id, entry.file_specific_info().md5());
 }