Add new UMA stats to get a handle on Downloads UI Usage

chrome/browser/history/history.h

Index: chrome/browser/history/history.h
diff --git a/chrome/browser/history/history.h b/chrome/browser/history/history.h
index 4c79d5dbbd6e75352b7a7fa275057e38140e5123..8874e103244edcae13858968b98857c660d93bcd 100644
--- a/chrome/browser/history/history.h
+++ b/chrome/browser/history/history.h
@@ -449,7 +449,10 @@ class HistoryService : public CancelableRequestProvider,
   // Called to update the history service about the current state of a download.
   // This is a 'fire and forget' query, so just pass the relevant state info to
   // the database with no need for a callback.
-  void UpdateDownload(int64 received_bytes, int32 state, int64 db_handle);
+  void UpdateDownload(int64 received_bytes,
+                      int32 state,
+                      const base::Time& end_time,
+                      int64 db_handle);
 
   // Called to update the history service about the path of a download.
   // This is a 'fire and forget' query.
@@ -466,6 +469,9 @@ class HistoryService : public CancelableRequestProvider,
   // both directions.
   void RemoveDownloadsBetween(base::Time remove_begin, base::Time remove_end);
 
+  // Sets the download record |opened| flag.
+  void MarkDownloadOpened(int64 db_handle);
+
   // Visit Segments ------------------------------------------------------------
 
   typedef Callback2<Handle, std::vector<PageUsageData*>*>::Type