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

content/browser/download/download_item.h

Index: content/browser/download/download_item.h
diff --git a/content/browser/download/download_item.h b/content/browser/download/download_item.h
index 2a9b8b94dc0f99d4d548acff788f28e144d3b0d5..5769bcc3a2e2356fa8320ba810bcf79210235d9a 100644
--- a/content/browser/download/download_item.h
+++ b/content/browser/download/download_item.h
@@ -278,6 +278,7 @@ class CONTENT_EXPORT DownloadItem {
   int32 id() const { return download_id_; }
   DownloadId global_id() const;
   base::Time start_time() const { return start_time_; }
+  base::Time end_time() const { return end_time_; }
   void set_db_handle(int64 handle) { db_handle_ = handle; }
   int64 db_handle() const { return db_handle_; }
   DownloadManager* download_manager() { return download_manager_; }
@@ -435,6 +436,9 @@ class CONTENT_EXPORT DownloadItem {
   // Time the download was started
   base::Time start_time_;
 
+  // Time the download completed
+  base::Time end_time_;
+
   // Our persistent store handle
   int64 db_handle_;