Move FileEnumerator to its own file, do some refactoring.

chrome/installer/util/shell_util_unittest.cc

Index: chrome/installer/util/shell_util_unittest.cc
diff --git a/chrome/installer/util/shell_util_unittest.cc b/chrome/installer/util/shell_util_unittest.cc
index aa3d8e9f11d0dc70e7f93436958f1ec507c45054..db38ed872b184c332fa05b15af4d13cc34e2423f 100644
--- a/chrome/installer/util/shell_util_unittest.cc
+++ b/chrome/installer/util/shell_util_unittest.cc
@@ -9,6 +9,7 @@
 #include "base/base_paths.h"
 #include "base/base_paths_win.h"
 #include "base/file_util.h"
+#include "base/files/file_enumerator.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/md5.h"
 #include "base/memory/scoped_ptr.h"
@@ -526,8 +527,8 @@ TEST_F(ShellUtilShortcutTest, CreateMultipleStartMenuShortcutsAndRemoveFolder) {
 
   base::FilePath shortcut_folder(
       fake_start_menu_.path().Append(dist_->GetAppShortCutName()));
-  file_util::FileEnumerator file_counter(shortcut_folder, false,
-                                         file_util::FileEnumerator::FILES);
+  base::FileEnumerator file_counter(shortcut_folder, false,
+                                    base::FileEnumerator::FILES);
   int count = 0;
   while (!file_counter.Next().empty())
     ++count;