Move FileEnumerator to its own file, do some refactoring.

content/browser/gpu/gpu_pixel_browsertest.cc

Index: content/browser/gpu/gpu_pixel_browsertest.cc
diff --git a/content/browser/gpu/gpu_pixel_browsertest.cc b/content/browser/gpu/gpu_pixel_browsertest.cc
index fb930761c8bd24600f275d9c7ea5522d43822366..f7f225462f7b54bb2b60741b465367e714283c5f 100644
--- a/content/browser/gpu/gpu_pixel_browsertest.cc
+++ b/content/browser/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_number_conversions.h"
@@ -398,10 +399,10 @@ class GpuPixelBrowserTest : public ContentBrowserTest {
   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();