wstring: use a few more FilePaths to remove Hack functions

chrome/installer/util/copy_tree_work_item.cc

 // Copyright (c) 2010 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/installer/util/copy_tree_work_item.h"
 
 #include <shlwapi.h>
 
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "chrome/installer/util/logging_installer.h"
 
 CopyTreeWorkItem::~CopyTreeWorkItem() {
   if (file_util::PathExists(backup_path_)) {
     file_util::Delete(backup_path_, true);
   }
 }
 
-CopyTreeWorkItem::CopyTreeWorkItem(const std::wstring& source_path,
-                                   const std::wstring& dest_path,
-                                   const std::wstring& temp_dir,
+CopyTreeWorkItem::CopyTreeWorkItem(const FilePath& source_path,
+                                   const FilePath& dest_path,
+                                   const FilePath& temp_dir,
                                    CopyOverWriteOption overwrite_option,
-                                   const std::wstring& alternative_path)
+                                   const FilePath& alternative_path)
     : source_path_(source_path),
       dest_path_(dest_path),
       temp_dir_(temp_dir),
       overwrite_option_(overwrite_option),
       alternative_path_(alternative_path),
       copied_to_dest_path_(false),
       moved_to_backup_(false),
       copied_to_alternate_path_(false) {
 }
 
@@ skipping 107 matching lines @@
     // Ideally we should not fail immediately. Instead we could try some
     // random paths under temp_dir_ until we reach certain limit.
     // For now our caller always provides a good temporary directory so
     // we don't bother.
     LOG(ERROR) << "backup path " << backup_path_.value() << " already exists";
     return false;
   }
 
   return true;
 }