wstring: use a few more FilePaths to remove Hack functions

chrome/installer/util/copy_tree_work_item.h

 // Copyright (c) 2009 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.
 
 #ifndef CHROME_INSTALLER_UTIL_COPY_TREE_WORK_ITEM_H_
 #define CHROME_INSTALLER_UTIL_COPY_TREE_WORK_ITEM_H_
 #pragma once
 
 #include <windows.h>
 
@@ skipping 19 matching lines @@
   virtual void Rollback();
 
  private:
   friend class WorkItem;
 
   // See comments on corresponding member variables for the semantics of
   // arguments.
   // Notes on temp_path: to facilitate rollback, the caller needs to supply
   // a temporary directory to save the original files if they exist under
   // dest_path.
-  CopyTreeWorkItem(const std::wstring& source_path,
-                   const std::wstring& dest_path,
-                   const std::wstring& temp_dir,
+  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);
 
   // Checks if the path specified is in use (and hence can not be deleted)
   bool IsFileInUse(const FilePath& path);
 
   // Get a backup path that can keep the original files under dest_path_,
   // and set backup_path_ with the result.
   bool GetBackupPath();
 
   // Source path to copy files from.
   FilePath source_path_;
@@ skipping 22 matching lines @@
   // Whether the source was copied to alternative_path_ because dest_path_
   // existed and was in use. Needed during rollback.
   bool copied_to_alternate_path_;
 
   // The full path in temporary directory that the original dest_path_ has
   // been moved to.
   FilePath backup_path_;
 };
 
 #endif  // CHROME_INSTALLER_UTIL_COPY_TREE_WORK_ITEM_H_