[Downloads] Ask DownloadHistory if a download was from history.

chrome/browser/download/download_history.h

Index: chrome/browser/download/download_history.h
diff --git a/chrome/browser/download/download_history.h b/chrome/browser/download/download_history.h
index e983c90964ff7cd3ab05215d9787b43e041e9c3f..8f998b9dc2778b0c6243e5e9030f3369e4f4437a 100644
--- a/chrome/browser/download/download_history.h
+++ b/chrome/browser/download/download_history.h
@@ -67,8 +67,11 @@ class DownloadHistory : public AllDownloadItemNotifier::Observer {
     virtual void OnDownloadHistoryDestroyed() {}
   };
 
-  // Returns true if the item is persisted.
-  static bool IsPersisted(content::DownloadItem* item);
+  // Returns true if the download is persisted. Not reliable when called from
+  // within a DownloadManager::Observer::OnDownloadCreated handler since the
+  // persisted state may not have been updated yet a download that were restored

[Randy Smith (Not in Mondays), 2014/04/10 18:03:23]

nit: "yet *for* a download"?

[asanka, 2014/04/17 21:16:10]

Done.

+  // from history.
+  static bool IsPersisted(const content::DownloadItem* item);
 
   // Neither |manager| nor |history| may be NULL.
   // DownloadService creates DownloadHistory some time after DownloadManager is
@@ -82,6 +85,14 @@ class DownloadHistory : public AllDownloadItemNotifier::Observer {
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
 
+  // Returns true if the download was restored from history. Safe to call from
+  // within a DownloadManager::Observer::OnDownloadCreated handler and can be
+  // used to distinguish between downloads that were created due to new requests
+  // vs. downloads that were created due to being restored from history. Note
+  // that the return value is only reliable for downloads that were restored by
+  // this specific DownloadHistory instance.

[Randy Smith (Not in Mondays), 2014/04/10 18:03:23]

Hmmm.  Not relevant for this CL, but I'm inclined to think that we should decide
whether we support multiple DownloadHistory instances (and not unless there's a
use case) and enforce that in the code.  It feels like the kind of thing that
could bit rot very easily (if we allow multiple instances but don't test them).

[asanka, 2014/04/17 21:16:10]

Yeah. Currently there's nothing that prevents multiple instances of
DownloadHistory from being associated with a single DownloadManager. There's
only one in practice.

+  bool WasRestoredFromHistory(const content::DownloadItem* item) const;
+
  private:
   typedef std::set<content::DownloadItem*> ItemSet;