Handle the case where IAttachmentExecute::Save() deletes a downloaded file.

content/browser/download/download_stats.h

Index: content/browser/download/download_stats.h
diff --git a/content/browser/download/download_stats.h b/content/browser/download/download_stats.h
index 3e5feb421dc1bc65b8efec40ff478810db6dba86..3bd47403c649c4a1d54eb9913a8bf97fef72df99 100644
--- a/content/browser/download/download_stats.h
+++ b/content/browser/download/download_stats.h
@@ -63,6 +63,10 @@ enum DownloadCountTypes {
   // progress.
   APPEND_TO_DETACHED_FILE_COUNT,
 
+  // Counts the number of instances where the downloaded file is missing after a
+  // successful invocation of win_util::ScanAndSaveDownloadedFile().
+  FILE_MISSING_AFTER_SUCCESSFUL_SCAN_COUNT,
+
   DOWNLOAD_COUNT_TYPES_LAST_ENTRY
 };