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

chrome/browser/history/history.cc

 // 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.
 
 // The history system runs on a background thread so that potentially slow
 // database operations don't delay the browser. This backend processing is
 // represented by HistoryBackend. The HistoryService's job is to dispatch to
 // that thread.
 //
 // Main thread                       History thread
@@ skipping 538 matching lines @@
 
 // Changes all IN_PROGRESS in the database entries to CANCELED.
 // IN_PROGRESS entries are the corrupted entries, not updated by next function
 // because of the crash or some other extremal exit.
 void HistoryService::CleanUpInProgressEntries() {
   ScheduleAndForget(PRIORITY_NORMAL, &HistoryBackend::CleanUpInProgressEntries);
 }
 
 // Handle updates for a particular download. This is a 'fire and forget'
 // operation, so we don't need to be called back.
-void HistoryService::UpdateDownload(int64 received_bytes,
-                                    int32 state,
-                                    int64 db_handle) {
-  ScheduleAndForget(PRIORITY_NORMAL, &HistoryBackend::UpdateDownload,
-                    received_bytes, state, db_handle);
+void HistoryService::UpdateDownload(const DownloadPersistentStoreInfo& data) {
+  ScheduleAndForget(PRIORITY_NORMAL, &HistoryBackend::UpdateDownload, data);
 }
 
 void HistoryService::UpdateDownloadPath(const FilePath& path,
                                         int64 db_handle) {
   ScheduleAndForget(PRIORITY_NORMAL, &HistoryBackend::UpdateDownloadPath,
                     path, db_handle);
 }
 
 void HistoryService::RemoveDownload(int64 db_handle) {
   ScheduleAndForget(PRIORITY_NORMAL,
@@ skipping 272 matching lines @@
     history::TopSites* ts = profile_->GetTopSitesWithoutCreating();
     if (ts)
       ts->MigrateFromHistory();
   }
 }
 
 void HistoryService::OnTopSitesReady() {
   ScheduleAndForget(PRIORITY_NORMAL,
                     &HistoryBackend::MigrateThumbnailsDatabase);
 }