Move FileEnumerator to its own file, do some refactoring.

chrome/browser/history/expire_history_backend.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.
 
 #include "chrome/browser/history/expire_history_backend.h"
 
 #include <algorithm>
 #include <functional>
 #include <limits>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
 #include "base/file_util.h"
+#include "base/files/file_enumerator.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "chrome/browser/bookmarks/bookmark_service.h"
 #include "chrome/browser/history/archived_database.h"
 #include "chrome/browser/history/history_database.h"
 #include "chrome/browser/history/history_notifications.h"
 #include "chrome/browser/history/text_database.h"
 #include "chrome/browser/history/text_database_manager.h"
 #include "chrome/browser/history/thumbnail_database.h"
 #include "chrome/common/chrome_notification_types.h"
@@ skipping 723 matching lines @@
   Time::Exploded exploded;
   Time::Now().LocalExplode(&exploded);
   int cutoff_month =
       exploded.year * 12 + exploded.month - kStoreHistoryIndexesForMonths;
   TextDatabase::DBIdent cutoff_id =
       (cutoff_month / 12) * 100 + (cutoff_month % 12);
 
   base::FilePath::StringType history_index_files_pattern =
       TextDatabase::file_base();
   history_index_files_pattern.append(FILE_PATH_LITERAL("*"));
-  file_util::FileEnumerator file_enumerator(
-      text_db_->GetDir(), false, file_util::FileEnumerator::FILES,
+  base::FileEnumerator file_enumerator(
+      text_db_->GetDir(), false, base::FileEnumerator::FILES,
       history_index_files_pattern);
   for (base::FilePath file = file_enumerator.Next(); !file.empty();
        file = file_enumerator.Next()) {
     TextDatabase::DBIdent file_id = TextDatabase::FileNameToID(file);
     if (file_id < cutoff_id)
       file_util::Delete(file, false);
   }
 }
 
 BookmarkService* ExpireHistoryBackend::GetBookmarkService() {
   // We use the bookmark service to determine if a URL is bookmarked. The
   // bookmark service is loaded on a separate thread and may not be done by the
   // time we get here. We therefor block until the bookmarks have finished
   // loading.
   if (bookmark_service_)
     bookmark_service_->BlockTillLoaded();
   return bookmark_service_;
 }
 
 }  // namespace history