Move FileEnumerator to its own file, do some refactoring.

chrome/test/chromedriver/util.cc

Index: chrome/test/chromedriver/util.cc
diff --git a/chrome/test/chromedriver/util.cc b/chrome/test/chromedriver/util.cc
index 60919aba3f7fc7bd1b36ee4b4584849b59dbacae..e4907b18f032f9b3ccbc49bb0b8a325f180894c8 100644
--- a/chrome/test/chromedriver/util.cc
+++ b/chrome/test/chromedriver/util.cc
@@ -6,6 +6,7 @@
 
 #include "base/base64.h"
 #include "base/file_util.h"
+#include "base/files/file_enumerator.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/format_macros.h"
 #include "base/rand_util.h"
@@ -383,9 +384,8 @@ Status UnzipSoleFile(const base::FilePath& unzip_dir,
     }
   }
 
-  file_util::FileEnumerator enumerator(unzip_dir, false /* recursive */,
-      file_util::FileEnumerator::FILES |
-      file_util::FileEnumerator::DIRECTORIES);
+  base::FileEnumerator enumerator(unzip_dir, false /* recursive */,
+      base::FileEnumerator::FILES | base::FileEnumerator::DIRECTORIES);
   base::FilePath first_file = enumerator.Next();
   if (first_file.empty())
     return Status(kUnknownError, "contained 0 files");