Use a direct include of strings headers in chrome_frame/.

chrome_frame/test/util_unittests.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 "base/file_version_info.h"
 #include "base/file_version_info_win.h"
 #include "base/files/file_path.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/win/registry.h"
 #include "chrome_frame/navigation_constraints.h"
 #include "chrome_frame/registry_list_preferences_holder.h"
 #include "chrome_frame/test/chrome_frame_test_utils.h"
 #include "chrome_frame/utils.h"
 
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 527 matching lines @@
 
       ASSERT_EQ(expect_match,
                 CheckXUaCompatibleDirective(test.header_value,
                                             all_versions[version_index]))
           << "Expect '" << test.header_value << "' to "
           << (expect_match ? "match" : "not match") << " IE major version "
           << all_versions[version_index];
     }
   }
 }