Eliminate the archived history database and clean up related code.

chrome/browser/history/history_service.cc

 // Copyright (c) 2012 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
 // -----------                       --------------
 // HistoryService <----------------> HistoryBackend
 //                                   -> HistoryDatabase
 //                                      -> SQLite connection to History
-//                                   -> ArchivedDatabase
-//                                      -> SQLite connection to Archived History
 //                                   -> ThumbnailDatabase
 //                                      -> SQLite connection to Thumbnails
 //                                         (and favicons)
 
 #include "chrome/browser/history/history_service.h"
 
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
@@ skipping 1142 matching lines @@
   DCHECK(thread_checker_.CalledOnValidThread());
   visit_database_observers_.RemoveObserver(observer);
 }
 
 void HistoryService::NotifyVisitDBObserversOnAddVisit(
     const history::BriefVisitInfo& info) {
   DCHECK(thread_checker_.CalledOnValidThread());
   FOR_EACH_OBSERVER(history::VisitDatabaseObserver, visit_database_observers_,
                     OnAddVisit(info));
 }