Move string files in base/ to the string subdirectory.

base/strings/string_util.cc

Index: base/strings/string_util.cc
diff --git a/base/string_util.cc b/base/strings/string_util.cc
similarity index 99%
rename from base/string_util.cc
rename to base/strings/string_util.cc
index bbded5737445be5ddb2a3359eac9d956d92fd493..ad49d5b5ea14bed9361b16419d8847347671f9cc 100644
--- a/base/string_util.cc
+++ b/base/strings/string_util.cc
@@ -2,9 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/string_util.h"
-
-#include "build/build_config.h"
+#include "base/strings/string_util.h"
 
 #include <ctype.h>
 #include <errno.h>
@@ -26,6 +24,7 @@
 #include "base/strings/utf_string_conversion_utils.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/third_party/icu/icu_utf.h"
+#include "build/build_config.h"
 
 namespace {