Downloads: Added transient flag to download item and download database

components/history/core/browser/download_database.h

Index: components/history/core/browser/download_database.h
diff --git a/components/history/core/browser/download_database.h b/components/history/core/browser/download_database.h
index 421218d9bbad452d5fcfd2398f7507171199a108..7a80f69eb00aab8f26836dc7753a16af6e308746 100644
--- a/components/history/core/browser/download_database.h
+++ b/components/history/core/browser/download_database.h
@@ -96,6 +96,9 @@ class DownloadDatabase {
   // Returns true if able to add last_access_time column to the download table.
   bool MigrateDownloadLastAccessTime();
 
+  // Returns true if able to add transient column to the download table.
+  bool MigrateDownloadTransient();
+
   // Creates the downloads table if needed.
   bool InitDownloadTable();