Automated IWYU fix for TaskRunner includes.

components/metrics/metrics_service.h

 // Copyright 2014 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.
 
 // This file defines a service that collects information about the user
 // experience in order to help improve future versions of the app.
 
 #ifndef COMPONENTS_METRICS_METRICS_SERVICE_H_
 #define COMPONENTS_METRICS_METRICS_SERVICE_H_
 
 #include <stdint.h>
 
 #include <map>
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_flattener.h"
 #include "base/metrics/histogram_snapshot_manager.h"
 #include "base/metrics/user_metrics.h"
 #include "base/observer_list.h"
+#include "base/single_thread_task_runner.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
 #include "components/metrics/clean_exit_beacon.h"
 #include "components/metrics/execution_phase.h"
 #include "components/metrics/metrics_log.h"
 #include "components/metrics/metrics_log_manager.h"
 #include "components/metrics/metrics_log_store.h"
 #include "components/metrics/metrics_provider.h"
 #include "components/metrics/metrics_reporting_service.h"
@@ skipping 399 matching lines @@
   // Weak pointers factory used to post task on different threads. All weak
   // pointers managed by this factory have the same lifetime as MetricsService.
   base::WeakPtrFactory<MetricsService> self_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsService);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_METRICS_SERVICE_H_