Use a direct include of strings headers in chrome/browser/i*/.

chrome/browser/io_thread.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/io_thread.h"
 
 #include <vector>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
 #include "base/debug/leak_tracker.h"
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
 #include "base/prefs/pref_registry_simple.h"
 #include "base/prefs/pref_service.h"
 #include "base/stl_util.h"
-#include "base/string_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
 #include "base/threading/thread.h"
 #include "base/threading/worker_pool.h"
 #include "base/time/default_tick_clock.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/event_router_forwarder.h"
 #include "chrome/browser/net/async_dns_field_trial.h"
 #include "chrome/browser/net/basic_http_user_agent_settings.h"
 #include "chrome/browser/net/chrome_net_log.h"
 #include "chrome/browser/net/chrome_network_delegate.h"
@@ skipping 919 matching lines @@
       base::FieldTrialList::FindFullName(kQuicFieldTrialName);
 
   if (command_line.HasSwitch(switches::kDisableQuic))
     return false;
 
   if (command_line.HasSwitch(switches::kEnableQuic))
     return true;
 
   return quic_trial_group == kQuicFieldTrialEnabledGroupName;
 }