Revert of Move JoinString to the base namespace

chrome/browser/sync_file_system/drive_backend/metadata_database.cc

 // Copyright 2013 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/sync_file_system/drive_backend/metadata_database.h"
 
 #include <algorithm>
 #include <stack>
 
 #include "base/bind.h"
@@ skipping 1725 matching lines @@
       dict->SetString("title", details.title());
       dict->SetString("type", FileKindToString(details.file_kind()));
       dict->SetString("md5", details.md5());
       dict->SetString("etag", details.etag());
       dict->SetString("missing", details.missing() ? "true" : "false");
       dict->SetString("change_id", base::Int64ToString(details.change_id()));
 
       std::vector<std::string> parents;
       for (int i = 0; i < details.parent_folder_ids_size(); ++i)
         parents.push_back(details.parent_folder_ids(i));
-      dict->SetString("parents", base::JoinString(parents, ","));
+      dict->SetString("parents", JoinString(parents, ","));
     }
     files->Append(dict);
   }
   return files.Pass();
 }
 
 void MetadataDatabase::AttachSyncRoot(
     const google_apis::FileResource& sync_root_folder) {
   scoped_ptr<FileMetadata> sync_root_metadata =
       CreateFileMetadataFromFileResource(
@@ skipping 44 matching lines @@
       return false;
 
   if (!parents.empty())
     return false;
 
   return true;
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system