Move FileEnumerator to its own file, do some refactoring.

chrome/browser/chromeos/camera_detector.cc

Index: chrome/browser/chromeos/camera_detector.cc
diff --git a/chrome/browser/chromeos/camera_detector.cc b/chrome/browser/chromeos/camera_detector.cc
index e7fddb92ef758a382993282f72ed17497efb415c..3d5d039ad3a7a658ad7188050db4868d28a6ea17 100644
--- a/chrome/browser/chromeos/camera_detector.cc
+++ b/chrome/browser/chromeos/camera_detector.cc
@@ -6,6 +6,7 @@
 
 #include "base/bind.h"
 #include "base/file_util.h"
+#include "base/files/file_enumerator.h"
 #include "base/location.h"
 #include "base/string_util.h"
 #include "base/strings/string_split.h"
@@ -66,10 +67,9 @@ void CameraDetector::OnPresenceCheckDone(const base::Closure& callback,
 bool CameraDetector::CheckPresence() {
   // We do a quick check using udev database because opening each /dev/videoX
   // device may trigger costly device initialization.
-  using file_util::FileEnumerator;
-  FileEnumerator file_enum(
+  base::FileEnumerator file_enum(
       base::FilePath(kV4LSubsystemDir), false /* not recursive */,
-      FileEnumerator::FILES | FileEnumerator::SHOW_SYM_LINKS);
+      base::FileEnumerator::FILES | base::FileEnumerator::SHOW_SYM_LINKS);
   for (base::FilePath path = file_enum.Next(); !path.empty();
        path = file_enum.Next()) {
     std::string v4l_capabilities;