Move FileEnumerator to its own file, do some refactoring.

chrome/browser/ui/webui/feedback_ui.cc

Index: chrome/browser/ui/webui/feedback_ui.cc
diff --git a/chrome/browser/ui/webui/feedback_ui.cc b/chrome/browser/ui/webui/feedback_ui.cc
index 1d09ab9a473bf3764ac3b2f52375525056494edb..30b12d05e3467bdf805c7951449f132ce7fbe717 100644
--- a/chrome/browser/ui/webui/feedback_ui.cc
+++ b/chrome/browser/ui/webui/feedback_ui.cc
@@ -10,6 +10,7 @@
 #include "base/base64.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
+#include "base/files/file_enumerator.h"
 #include "base/logging.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop.h"
@@ -704,9 +705,8 @@ void FeedbackUI::GetMostRecentScreenshots(
   std::string pattern =
       std::string(ScreenshotSource::kScreenshotPrefix) + "*" +
                   ScreenshotSource::kScreenshotSuffix;
-  file_util::FileEnumerator screenshots(filepath, false,
-                                        file_util::FileEnumerator::FILES,
-                                        pattern);
+  base::FileEnumerator screenshots(filepath, false,
+                                   base::FileEnumerator::FILES, pattern);
   base::FilePath screenshot = screenshots.Next();
 
   std::vector<std::string> screenshot_filepaths;