Use a direct include of strings headers in base/.

BUG=247723
TEST=none
TBR=ben@chromium.org

Review URL: https://chromiumcodereview.appspot.com/16745002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@205530 0039d316-1c4b-4281-b951-d872f2087c98

diff --git a/base/file_util.cc b/base/file_util.cc
index 0d531621..8e0fbb64 100644
--- a/base/file_util.cc
+++ b/base/file_util.cc

@@ -14,9 +14,9 @@
 #include "base/files/file_enumerator.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
-#include "base/string_util.h"
-#include "base/stringprintf.h"
 #include "base/strings/string_piece.h"
+#include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
 #include "base/strings/utf_string_conversions.h"
 
 using base::FileEnumerator;