Revert of Delete base/prefs and update callers to use components.

ios/chrome/browser/ios_chrome_io_thread.cc

 // Copyright 2015 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 "ios/chrome/browser/ios_chrome_io_thread.h"
 
 #include <stddef.h>
 
 #include <utility>
 #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/environment.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/metrics/field_trial.h"
+#include "base/prefs/pref_service.h"
 #include "base/stl_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "base/threading/thread.h"
 #include "base/threading/worker_pool.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
 #include "components/data_reduction_proxy/core/common/data_reduction_proxy_params.h"
 #include "components/net_log/chrome_net_log.h"
-#include "components/prefs/pref_service.h"
 #include "components/proxy_config/pref_proxy_config_tracker.h"
 #include "components/variations/variations_associated_data.h"
 #include "components/version_info/version_info.h"
 #include "ios/chrome/browser/chrome_switches.h"
 #include "ios/chrome/browser/net/cookie_util.h"
 #include "ios/chrome/browser/net/ios_chrome_network_delegate.h"
 #include "ios/chrome/browser/net/proxy_service_factory.h"
 #include "ios/chrome/common/channel_info.h"
 #include "ios/web/public/user_agent.h"
 #include "ios/web/public/web_client.h"
@@ skipping 1002 matching lines @@
 
   globals->system_http_network_session.reset(
       new net::HttpNetworkSession(system_params));
   globals->system_http_transaction_factory.reset(
       new net::HttpNetworkLayer(globals->system_http_network_session.get()));
   context->set_http_transaction_factory(
       globals->system_http_transaction_factory.get());
 
   return context;
 }