Use a direct include of strings headers in base/.

BUG=247723
TEST=none
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Review URL: https://chromiumcodereview.appspot.com/16320009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@205284 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/base/version.cc b/base/version.cc
index eb1806e..79693f7 100644
--- a/base/version.cc
+++ b/base/version.cc
@@ -7,9 +7,9 @@
 #include <algorithm>
 
 #include "base/logging.h"
-#include "base/string_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
 
 namespace base {