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

content/browser/download/download_persistent_store_info.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Download struct used for informing and querying the download system's
 // persitent store.
 
 #ifndef CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_PERSISTENT_STORE_INFO_H_
 #define CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_PERSISTENT_STORE_INFO_H_
 #pragma once
 
 #include <vector>
 
 #include "base/file_path.h"
 #include "base/time.h"
 #include "content/common/content_export.h"
 #include "googleurl/src/gurl.h"
 
 class DownloadItem;
 
 // Contains the information that is stored in the download system's persistent
-// store (or refers to it).  Managed by the DownloadItem.
+// store (or refers to it).  Managed by the DownloadItem.  When used to create a
+// history entry, all fields except for |db_handle| are set by DownloadItem and
+// read by DownloadDatabase.  When used to update a history entry, DownloadItem
+// sets all fields, but DownloadDatabase only reads |end_time|,
+// |received_bytes|, |state|, and |opened|, and uses |db_handle| to select the
+// row in the database table to update.  When used to load DownloadItems from
+// the history, all fields except |referrer_url| are set by the DownloadDatabase
+// and read by the DownloadItem.
 struct CONTENT_EXPORT DownloadPersistentStoreInfo {
   // TODO(ahendrickson) -- Reduce the number of constructors.
   DownloadPersistentStoreInfo();
   DownloadPersistentStoreInfo(const FilePath& path,
                               const GURL& url,
                               const GURL& referrer,
                               const base::Time& start,
+                              const base::Time& end,
                               int64 received,
                               int64 total,
                               int32 download_state,
-                              int64 handle);
+                              int64 handle,
+                              bool download_opened);
   ~DownloadPersistentStoreInfo();  // For linux-clang.
 
   // The final path where the download is saved.
   FilePath path;
 
   // The URL from which we are downloading. This is the final URL after any
-  // redirection by the server for |url_chain|.
+  // redirection by the server for |url_chain|. Is not changed by UpdateEntry().
   GURL url;
 
   // The URL that referred us.
   GURL referrer_url;
 
-  // The time when the download started.
+  // The time when the download started. Is not changed by UpdateEntry().
   base::Time start_time;
 
+  // The time when the download completed.
+  base::Time end_time;
+
   // The number of bytes received (so far).
   int64 received_bytes;
 
-  // The total number of bytes in the download.
+  // The total number of bytes in the download. Is not changed by UpdateEntry().
   int64 total_bytes;
 
   // The current state of the download.
   int32 state;
 
-  // The handle of the download in the database.
+  // The handle of the download in the database. Is not changed by
+  // UpdateEntry().
   int64 db_handle;
+
+  // Whether this download has ever been opened from the browser.
+  bool opened;
 };
 
 #endif  // CONTENT_BROWSER_DOWNLOAD_DOWNLOAD_PERSISTENT_STORE_INFO_H_