Move FileEnumerator to its own file, do some refactoring.

chrome/installer/util/duplicate_tree_detector.cc

 // Copyright (c) 2011 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/duplicate_tree_detector.h"
 
 #include "base/file_util.h"
+#include "base/files/file_enumerator.h"
 #include "base/logging.h"
 
 namespace installer {
 
 bool IsIdenticalFileHierarchy(const base::FilePath& src_path,
                               const base::FilePath& dest_path) {
-  using file_util::FileEnumerator;
   base::PlatformFileInfo src_info;
   base::PlatformFileInfo dest_info;
 
   bool is_identical = false;
   if (file_util::GetFileInfo(src_path, &src_info) &&
       file_util::GetFileInfo(dest_path, &dest_info)) {
     // Both paths exist, check the types:
     if (!src_info.is_directory && !dest_info.is_directory) {
       // Two files are "identical" if the file sizes are equivalent.
       is_identical = src_info.size == dest_info.size;
 #ifndef NDEBUG
       // For Debug builds, also check last modification time (to make sure
       // version dir DLLs are replaced on over-install even if the tested change
       // doesn't happen to change a given DLL's size).
       if (is_identical)
         is_identical = (src_info.last_modified == dest_info.last_modified);
 #endif
     } else if (src_info.is_directory && dest_info.is_directory) {
       // Two directories are "identical" if dest_path contains entries that are
       // "identical" to all the entries in src_path.
       is_identical = true;
 
-      FileEnumerator path_enum(src_path, false /* not recursive */,
-          FileEnumerator::FILES | FileEnumerator::DIRECTORIES);
+      base::FileEnumerator path_enum(src_path, false /* not recursive */,
+          base::FileEnumerator::FILES | base::FileEnumerator::DIRECTORIES);
       for (base::FilePath path = path_enum.Next();
            is_identical && !path.empty();
            path = path_enum.Next()) {
         is_identical =
             IsIdenticalFileHierarchy(path, dest_path.Append(path.BaseName()));
       }
     } else {
       // The two paths are of different types, so they cannot be identical.
       DCHECK(!is_identical);
     }
   }
 
   return is_identical;
 }
 
 }  // namespace installer