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>
+#include <string>
 
 #include "base/threading/platform_thread.h"
 #include "chrome/browser/history/history_types.h"
 #include "sql/meta_table.h"
 
 struct DownloadPersistentStoreInfo;
 class FilePath;
 
 namespace sql {
 class Connection;
 }
 
 namespace history {
 
 // Maintains a table of downloads.
 class DownloadDatabase {
  public:
   // 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);
+  // Does not update |url|, |start_time|, |total_bytes|; uses |db_handle| only
+  // to select the row in the database table to update.
+  bool UpdateDownload(const DownloadPersistentStoreInfo& data);
 
   // 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();
 
@@ skipping 14 matching lines @@
   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();
 
  private:
+  bool EnsureColumnExists(const std::string& name, const std::string& type);
+
   // 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_;
 
   DISALLOW_COPY_AND_ASSIGN(DownloadDatabase);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_DOWNLOAD_DATABASE_H_