Use a direct include of strings headers in chrome/browser/chromeos/.

chrome/browser/chromeos/proxy_config_service_impl_unittest.cc

 // Copyright (c) 2012 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 "chrome/browser/chromeos/proxy_config_service_impl.h"
 
 #include <vector>
 
 #include "base/format_macros.h"
 #include "base/json/json_writer.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "base/prefs/testing_pref_service.h"
-#include "base/stringprintf.h"
+#include "base/strings/stringprintf.h"
 #include "chrome/browser/chromeos/settings/cros_settings.h"
 #include "chrome/browser/chromeos/settings/device_settings_service.h"
 #include "chrome/browser/chromeos/ui_proxy_config.h"
 #include "chrome/common/pref_names.h"
 #include "chromeos/dbus/dbus_thread_manager.h"
 #include "chromeos/dbus/shill_profile_client.h"
 #include "chromeos/dbus/shill_service_client.h"
 #include "chromeos/network/network_handler.h"
 #include "chromeos/network/network_state.h"
 #include "chromeos/network/network_state_handler.h"
@@ skipping 418 matching lines @@
     pref_service_.RemoveRecommendedPref(prefs::kProxy);
     SyncGetLatestProxyConfig(&actual_config);
     EXPECT_EQ(network_params.auto_detect, actual_config.auto_detect());
     EXPECT_EQ(network_params.pac_url, actual_config.pac_url());
     EXPECT_TRUE(network_params.proxy_rules.Matches(
         actual_config.proxy_rules()));
   }
 }
 
 }  // namespace chromeos