Move FileEnumerator to its own file, do some refactoring.

chrome/test/gpu/gpu_pixel_browsertest.cc

Index: chrome/test/gpu/gpu_pixel_browsertest.cc
diff --git a/chrome/test/gpu/gpu_pixel_browsertest.cc b/chrome/test/gpu/gpu_pixel_browsertest.cc
index 17527131ebc982c081afd7b4a0bbf37b984298e4..82e997e667109927e5ea9dde67de9b449e3a7c0a 100644
--- a/chrome/test/gpu/gpu_pixel_browsertest.cc
+++ b/chrome/test/gpu/gpu_pixel_browsertest.cc
@@ -4,6 +4,7 @@
 
 #include "base/command_line.h"
 #include "base/file_util.h"
+#include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
 #include "base/path_service.h"
 #include "base/string_util.h"
@@ -420,10 +421,10 @@ class GpuPixelBrowserTest : public InProcessBrowserTest {
   void ObtainLocalRefImageRevision() {
     base::FilePath filter;
     filter = filter.AppendASCII(test_name_ + "_*.rev");
-    file_util::FileEnumerator locator(ref_img_dir_,
-                                      false,  // non recursive
-                                      file_util::FileEnumerator::FILES,
-                                      filter.value());
+    base::FileEnumerator locator(ref_img_dir_,
+                                 false,  // non recursive
+                                 base::FileEnumerator::FILES,
+                                 filter.value());
     int64 max_revision = 0;
     std::vector<base::FilePath> outdated_revs;
     for (base::FilePath full_path = locator.Next();