Downloads: Added transient flag to download item and download database

content/public/browser/download_item.h

Index: content/public/browser/download_item.h
diff --git a/content/public/browser/download_item.h b/content/public/browser/download_item.h
index af9715db4f0ff9dcd54e5c5dcc4bf5a10a4539c2..8fd6f03f36ff7a5272105393d68e40681b2a7b1a 100644
--- a/content/public/browser/download_item.h
+++ b/content/public/browser/download_item.h
@@ -400,6 +400,9 @@ class CONTENT_EXPORT DownloadItem : public base::SupportsUserData {
   // been opened.
   virtual base::Time GetLastAccessTime() const = 0;
 
+  // Returns whether the download item should be visible.
+  virtual bool IsVisible() const = 0;
+
   //    Misc State accessors ---------------------------------------------------
 
   // BrowserContext that indirectly owns this download. Always valid.