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

chrome/browser/history/download_database.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.
 
 #ifndef CHROME_BROWSER_HISTORY_DOWNLOAD_DATABASE_H_
 #define CHROME_BROWSER_HISTORY_DOWNLOAD_DATABASE_H_
 #pragma once
 
 #include <set>
 
@@ skipping 16 matching lines @@
   // Must call InitDownloadTable before using any other functions.
   DownloadDatabase();
   virtual ~DownloadDatabase();
 
   int next_download_id() const { return next_id_; }
 
   // Get all the downloads from the database.
   void QueryDownloads(std::vector<DownloadPersistentStoreInfo>* results);
 
   // Update the state of one download. Returns true if successful.
-  bool UpdateDownload(int64 received_bytes, int32 state, DownloadID db_handle);
+  bool UpdateDownload(int64 received_bytes, int32 state,
+                      const base::Time& end_time, DownloadID db_handle);
 
   // Update the path of one download. Returns true if successful.
   bool UpdateDownloadPath(const FilePath& path, DownloadID db_handle);
 
   // Fixes state of the download entries. Sometimes entries with IN_PROGRESS
   // state are not updated during browser shutdown (particularly when crashing).
   // On the next start such entries are considered canceled. This functions
   // fixes such entries.
   bool CleanUpInProgressEntries();
 
   // Create a new database entry for one download and return its primary db id.
   int64 CreateDownload(const DownloadPersistentStoreInfo& info);
 
   // Remove a download from the database.
   void RemoveDownload(DownloadID db_handle);
 
   // Remove all completed downloads that started after |remove_begin|
   // (inclusive) and before |remove_end|. You may use null Time values
   // to do an unbounded delete in either direction. This function ignores
   // all downloads that are in progress or are waiting to be cancelled.
   void RemoveDownloadsBetween(base::Time remove_begin, base::Time remove_end);
 
+  // Set the |opened| flag to true.
+  void MarkDownloadOpened(DownloadID db_handle);
+
  protected:
   // Returns the database for the functions in this interface.
   virtual sql::Connection& GetDB() = 0;
 
   // Creates the downloads table if needed.
   bool InitDownloadTable();
 
   // Used to quickly clear the downloads. First you would drop it, then you
   // would re-initialize it.
   bool DropDownloadTable();
 
+  bool MaybeUpgradeDownloadsSchema();
+
+  bool CreateDownloadsTable();
+
+  enum DownloadsSchemaVersion {
+    DOWNLOADS_SCHEMA_VERSION_UNINITIALIZED = -1,
+    DOWNLOADS_SCHEMA_VERSION_BASE = 0,
+    DOWNLOADS_SCHEMA_VERSION_OPENED = 1,
+    // Add new schema versions here with explicit numbers, update kCurrent, and
+    // support your new version in CreateDownloadsTable,
+    // MaybeUpgradeDownloadsSchema, and QueryDownloads.
+  };
+  static const DownloadsSchemaVersion kCurrentDownloadsSchemaVersion =
+    DOWNLOADS_SCHEMA_VERSION_OPENED;
+
+  DownloadsSchemaVersion downloads_schema_version() const {
+    return schema_version_;
+  }
+
  private:
   // TODO(rdsmith): Remove after http://crbug.com/96627 has been resolved.
   std::set<int64> returned_ids_;
   bool owning_thread_set_;
   base::PlatformThreadId owning_thread_;
 
   int next_id_;
   sql::MetaTable meta_table_;
+  DownloadsSchemaVersion schema_version_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadDatabase);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_DOWNLOAD_DATABASE_H_