Use a direct include of strings headers in chrome/test/.

chrome/test/ppapi/ppapi_test.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/test/ppapi/ppapi_test.h"
 
 #include "base/command_line.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/path_service.h"
-#include "base/string_util.h"
-#include "base/stringprintf.h"
+#include "base/strings/string_util.h"
+#include "base/strings/stringprintf.h"
 #include "base/test/test_timeouts.h"
 #include "build/build_config.h"
 #include "chrome/browser/content_settings/host_content_settings_map.h"
 #include "chrome/browser/infobars/confirm_infobar_delegate.h"
 #include "chrome/browser/infobars/infobar.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_tabstrip.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/chrome_notification_types.h"
@@ skipping 347 matching lines @@
     const std::string& base,
     const std::string& test_case) {
   return base::StringPrintf("%smode=nacl_newlib&testcase=%s", base.c_str(),
                             test_case.c_str());
 }
 
 void PPAPIBrokerInfoBarTest::SetUpOnMainThread() {
   // The default content setting for the PPAPI broker is ASK. We purposefully
   // don't call PPAPITestBase::SetUpOnMainThread() to keep it that way.
 }