For downloads requiring a user gesture, also require...

chrome/browser/download/download_state_info.h

Index: chrome/browser/download/download_state_info.h
===================================================================
--- chrome/browser/download/download_state_info.h	(revision 86341)
+++ chrome/browser/download/download_state_info.h	(working copy)
@@ -11,6 +11,7 @@
 // Contains information relating to the process of determining what to do with
 // the download.
 struct DownloadStateInfo {
+  enum Tristate { NO = 0, YES, UNKNOWN, };
   DownloadStateInfo();
   DownloadStateInfo(bool has_user_gesture,
                     bool prompt_user_for_save_location);
@@ -20,7 +21,8 @@
                     bool prompt_user_for_save_location,
                     int uniquifier,
                     bool dangerous_file,
-                    bool dangerous_url,
+                    Tristate dangerous_url,
+                    Tristate visited_referrer_before,
                     bool extension_install);
 
   // Indicates if the download is dangerous.
@@ -50,8 +52,11 @@
   bool is_dangerous_file;
 
   // If safebrowsing believes this URL leads to malware.
-  bool is_dangerous_url;
+  Tristate is_dangerous_url;
 
+  // If the user has visited the page hosting the download before today.
+  Tristate visited_referrer_before;
+
   // True if this download is for extension install.
   bool is_extension_install;