Use a direct include of strings headers in x/.

chrome/browser/ui/views/tabs/stacked_tab_strip_layout_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/ui/views/tabs/stacked_tab_strip_layout.h"
 
 #include <string>
 
-#include "base/string_util.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/views/view.h"
 #include "ui/views/view_model.h"
 
 namespace {
 
 struct CommonTestData {
   const int initial_x;
   const int width;
   const int tab_size;
@@ skipping 530 matching lines @@
     // Location can be honored.
     { { 0, 300, 100, -10, 2, 0, 3, "", "0 2 4 40 130 198 200" }, 40 },
   };
   for (size_t i = 0; i < ARRAYSIZE_UNSAFE(test_data); ++i) {
     CreateLayout(test_data[i].common_data);
     layout_->SetActiveTabLocation(test_data[i].location);
     EXPECT_EQ(test_data[i].common_data.expected_bounds, BoundsString()) <<
         " at " << i;
   }
 }