Use a direct include of strings headers in content/renderer and content/shell.

content/renderer/stats_collection_controller.cc

 // Copyright 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.
 
 #include "content/renderer/stats_collection_controller.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/json/json_writer.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/statistics_recorder.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "content/common/child_process_messages.h"
 #include "content/renderer/render_view_impl.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebFrame.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebView.h"
 
 using webkit_glue::CppArgumentList;
 using webkit_glue::CppVariant;
 
 namespace content {
 
@@ skipping 127 matching lines @@
   }
 
   std::string tab_timing_json;
   ConvertLoadTimeToJSON(
       observer->load_start_time(), observer->load_stop_time(),
       &tab_timing_json);
   result->Set(tab_timing_json);
 }
 
 }  // namespace content