Move FileEnumerator to its own file, do some refactoring.

chrome/common/extensions/api/i18n/default_locale_handler.cc

Index: chrome/common/extensions/api/i18n/default_locale_handler.cc
diff --git a/chrome/common/extensions/api/i18n/default_locale_handler.cc b/chrome/common/extensions/api/i18n/default_locale_handler.cc
index a8cd544b7623e6d7971c1cb68b93d9665da7109a..7221b8f91b16801fb4ea063fe4d94467d992f04f 100644
--- a/chrome/common/extensions/api/i18n/default_locale_handler.cc
+++ b/chrome/common/extensions/api/i18n/default_locale_handler.cc
@@ -5,6 +5,7 @@
 #include "chrome/common/extensions/api/i18n/default_locale_handler.h"
 
 #include "base/file_util.h"
+#include "base/files/file_enumerator.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
@@ -71,9 +72,7 @@ bool DefaultLocaleHandler::Validate(
   }
 
   // Treat all folders under _locales as valid locales.
-  file_util::FileEnumerator locales(path,
-                                    false,
-                                    file_util::FileEnumerator::DIRECTORIES);
+  base::FileEnumerator locales(path, false, base::FileEnumerator::DIRECTORIES);
 
   std::set<std::string> all_locales;
   extension_l10n_util::GetAllLocales(&all_locales);