Downloads: Added transient flag to download item and download database

components/history/core/browser/download_row.h

Index: components/history/core/browser/download_row.h
diff --git a/components/history/core/browser/download_row.h b/components/history/core/browser/download_row.h
index cb0f0cc83862d4f9ce3d742460486b3de100291f..d6320407a580b41ede56bcd5c35aa90098fc8427 100644
--- a/components/history/core/browser/download_row.h
+++ b/components/history/core/browser/download_row.h
@@ -47,6 +47,7 @@ struct DownloadRow {
               const std::string& guid,
               bool download_opened,
               base::Time last_access,
+              bool transient,
               const std::string& ext_id,
               const std::string& ext_name,
               const std::vector<DownloadSliceInfo>& download_slice_info);
@@ -138,6 +139,10 @@ struct DownloadRow {
   // The time when the download was last accessed.
   base::Time last_access_time;
 
+  // Whether this download is transient. Transient items are cleaned up after
+  // completion and not shown in the UI.
+  bool transient;
+
   // The id and name of the extension that created this download.
   std::string by_ext_id;
   std::string by_ext_name;