Use a direct include of strings headers in testing/, third_party/, tools/.

tools/set_default_handler/set_default_handler_main.cc

 // Copyright (c) 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.
 
 // Makes a given program ("Google Chrome" by default) the default handler for
 // some URL protocol ("http" by default) on Windows 8. These defaults can be
 // overridden via the --program and --protocol command line switches.
 
 #include <windows.h>
 
 #include "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/logging.h"
-#include "base/string16.h"
-#include "base/string_util.h"
+#include "base/strings/string16.h"
+#include "base/strings/string_util.h"
 #include "ui/base/win/atl_module.h"
 #include "win8/test/open_with_dialog_controller.h"
 
 namespace {
 
 const char kSwitchProgram[] = "program";
 const char kSwitchProtocol[] = "protocol";
 const wchar_t kDefaultProgram[] = L"Google Chrome";
 const wchar_t kDefaultProtocol[] = L"http";
 
@@ skipping 31 matching lines @@
     printf("success\n");
   } else if (!choices.empty()) {
     printf("failed to set program. possible choices: %ls\n",
            JoinString(choices, L", ").c_str());
   } else {
     printf("failed with HRESULT: 0x08X\n", result);
   }
 
   return FAILED(result);
 }