Move FileEnumerator to its own file, do some refactoring.

chrome/installer/util/installer_state_unittest.cc

Index: chrome/installer/util/installer_state_unittest.cc
diff --git a/chrome/installer/util/installer_state_unittest.cc b/chrome/installer/util/installer_state_unittest.cc
index 0f985f889c5c4923e5a2bad850b8d10270f7fc8e..f07564c743f12c5b5ff4dde88d1dfa14ada9f390 100644
--- a/chrome/installer/util/installer_state_unittest.cc
+++ b/chrome/installer/util/installer_state_unittest.cc
@@ -9,6 +9,7 @@
 #include "base/base_paths.h"
 #include "base/command_line.h"
 #include "base/file_util.h"
+#include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/path_service.h"
@@ -584,8 +585,8 @@ TEST_F(InstallerStateTest, RemoveOldVersionDirs) {
   expected_remaining_dirs.insert(kNewChromeExeVersion);
 
   // Enumerate dirs in target_path(), ensure only desired remain.
-  file_util::FileEnumerator version_enum(installer_state.target_path(), false,
-      file_util::FileEnumerator::DIRECTORIES);
+  base::FileEnumerator version_enum(installer_state.target_path(), false,
+                                    base::FileEnumerator::DIRECTORIES);
   for (base::FilePath next_version = version_enum.Next(); !next_version.empty();
        next_version = version_enum.Next()) {
     base::FilePath dir_name(next_version.BaseName());