Revert of Remove header dependencies from sequence_checker.h to sequenced_worker_pool.h

ios/chrome/browser/metrics/ios_chrome_metrics_service_client.mm

 // 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/metrics/ios_chrome_metrics_service_client.h"
 
 #include <stdint.h>
 
 #include <utility>
 #include <vector>
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/process/process_metrics.h"
 #include "base/rand_util.h"
 #include "base/strings/string16.h"
 #include "base/threading/platform_thread.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "components/browser_sync/profile_sync_service.h"
 #include "components/crash/core/common/crash_keys.h"
 #include "components/history/core/browser/history_service.h"
 #include "components/keyed_service/core/service_access_type.h"
 #include "components/metrics/call_stack_profile_metrics_provider.h"
 #include "components/metrics/drive_metrics_provider.h"
 #include "components/metrics/metrics_pref_names.h"
 #include "components/metrics/metrics_reporting_default_state.h"
 #include "components/metrics/metrics_service.h"
 #include "components/metrics/net/cellular_logic_helper.h"
@@ skipping 334 matching lines @@
 void IOSChromeMetricsServiceClient::OnSyncPrefsChanged(bool must_purge) {
   if (!ukm_service_)
     return;
   if (must_purge) {
     ukm_service_->Purge();
     ukm_service_->ResetClientId();
   }
   // Signal service manager to enable/disable UKM based on new state.
   UpdateRunningServices();
 }