Use a direct include of strings headers in chromeos/.

chromeos/ime/extension_ime_util.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chromeos/ime/extension_ime_util.h"
 
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 
 namespace chromeos {
 namespace {
 const char* kExtensionIMEPrefix = "_ext_ime_";
 }  // namespace
 
 namespace extension_ime_util {
 std::string GetInputMethodID(const std::string& extension_id,
                              const std::string& engine_id) {
   DCHECK(!extension_id.empty());
   DCHECK(!engine_id.empty());
   return kExtensionIMEPrefix + extension_id + engine_id;
 }
 
 bool IsExtensionIME(const std::string& input_method_id) {
   return StartsWithASCII(input_method_id,
                          kExtensionIMEPrefix,
                          true);  // Case sensitive.
 }
 
 bool IsMemberOfExtension(const std::string& input_method_id,
                          const std::string& extension_id) {
   return StartsWithASCII(input_method_id,
                          kExtensionIMEPrefix + extension_id,
                          true);  // Case sensitive.
 }
 
 }  // namespace extension_ime_util
 }  // namespace chromeos