Implement safebrowsing download feedback service, enabled for dev & canary only.

chrome/browser/download/download_item_model.h

Index: chrome/browser/download/download_item_model.h
diff --git a/chrome/browser/download/download_item_model.h b/chrome/browser/download/download_item_model.h
index 66021d3c7e4d8df174a68bea8523c674260ae485..157024f327fd3b31b93f417281c32edcf2732d91 100644
--- a/chrome/browser/download/download_item_model.h
+++ b/chrome/browser/download/download_item_model.h
@@ -79,6 +79,9 @@ class DownloadItemModel {
   // Is this considered a malicious download? Implies IsDangerous().
   bool IsMalicious() const;
 
+  // Is safe browsing download feedback feature available for this download?
+  bool ShouldAllowDownloadFeedback() const;
+
   // Returns |true| if this download is expected to complete successfully and
   // thereafter be removed from the shelf.  Downloads that are opened
   // automatically or are temporary will be removed from the shelf on successful