[Cleanup] Migrate the FileMetricsProvider to use the Task Scheduler.

chrome/browser/metrics/chrome_metrics_service_client.cc

 // 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.
 
 #include "chrome/browser/metrics/chrome_metrics_service_client.h"
 
 #include <stddef.h>
 
 #include <set>
 #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/files/file_util.h"
 #include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/field_trial_params.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/persistent_histogram_allocator.h"
 #include "base/metrics/persistent_memory_allocator.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/path_service.h"
 #include "base/rand_util.h"
 #include "base/strings/string16.h"
 #include "base/task_scheduler/post_task.h"
+#include "base/task_scheduler/task_traits.h"
 #include "base/threading/platform_thread.h"
-#include "base/threading/sequenced_worker_pool.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/google/google_brand.h"
 #include "chrome/browser/history/history_service_factory.h"
 #include "chrome/browser/metrics/chrome_metrics_service_accessor.h"
 #include "chrome/browser/metrics/chrome_stability_metrics_provider.h"
 #include "chrome/browser/metrics/https_engagement_metrics_provider.h"
 #include "chrome/browser/metrics/metrics_reporting_state.h"
@@ skipping 130 matching lines @@
 }
 
 // Constructs the name of a persistent metrics file from a directory and metrics
 // name, and either registers that file as associated with a previous run if
 // metrics reporting is enabled, or deletes it if not.
 void RegisterOrRemovePreviousRunMetricsFile(
     bool metrics_reporting_enabled,
     const base::FilePath& dir,
     base::StringPiece metrics_name,
     metrics::FileMetricsProvider::SourceAssociation association,
-    scoped_refptr<base::TaskRunner> task_runner,
     metrics::FileMetricsProvider* file_metrics_provider) {
   base::FilePath metrics_file;
   base::GlobalHistogramAllocator::ConstructFilePaths(
       dir, metrics_name, &metrics_file, nullptr, nullptr);
 
   if (metrics_reporting_enabled) {
     // Enable reading any existing saved metrics.
     file_metrics_provider->RegisterSource(
         metrics_file,
         metrics::FileMetricsProvider::SOURCE_HISTOGRAMS_ATOMIC_FILE,
         association, metrics_name);
   } else {
     // When metrics reporting is not enabled, any existing file should be
     // deleted in order to preserve user privacy.
-    task_runner->PostTask(FROM_HERE,
-                          base::BindOnce(base::IgnoreResult(&base::DeleteFile),
-                                         metrics_file, /*recursive=*/false));
+    base::PostTaskWithTraits(
+        FROM_HERE,
+        {base::MayBlock(), base::TaskPriority::BACKGROUND,
+         base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN},
+        base::BindOnce(base::IgnoreResult(&base::DeleteFile), metrics_file,
+                       /*recursive=*/false));
   }
 }
 
 std::unique_ptr<metrics::FileMetricsProvider> CreateFileMetricsProvider(
     bool metrics_reporting_enabled) {
-  // Fetch a worker-pool for performing I/O tasks that are not allowed on
-  // the main UI thread.
-  scoped_refptr<base::TaskRunner> task_runner =
-      content::BrowserThread::GetBlockingPool()
-          ->GetTaskRunnerWithShutdownBehavior(
-              base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN);
-
   // Create an object to monitor files of metrics and include them in reports.
   std::unique_ptr<metrics::FileMetricsProvider> file_metrics_provider(
-      new metrics::FileMetricsProvider(task_runner,
-                                       g_browser_process->local_state()));
+      new metrics::FileMetricsProvider(g_browser_process->local_state()));
 
   base::FilePath user_data_dir;
   if (base::PathService::Get(chrome::DIR_USER_DATA, &user_data_dir)) {
     // Register the Crashpad metrics files.
     // Register the data from the previous run if crashpad_handler didn't exit
     // cleanly.
     RegisterOrRemovePreviousRunMetricsFile(
         metrics_reporting_enabled, user_data_dir,
         kCrashpadHistogramAllocatorName,
         metrics::FileMetricsProvider::
             ASSOCIATE_INTERNAL_PROFILE_OR_PREVIOUS_RUN,
-        task_runner, file_metrics_provider.get());
+        file_metrics_provider.get());
 
     base::FilePath browser_metrics_upload_dir = user_data_dir.AppendASCII(
         ChromeMetricsServiceClient::kBrowserMetricsName);
     if (metrics_reporting_enabled) {
       file_metrics_provider->RegisterSource(
           browser_metrics_upload_dir,
           metrics::FileMetricsProvider::SOURCE_HISTOGRAMS_ATOMIC_DIR,
           metrics::FileMetricsProvider::ASSOCIATE_INTERNAL_PROFILE,
           ChromeMetricsServiceClient::kBrowserMetricsName);
 
@@ skipping 775 matching lines @@
     ukm_service_->Purge();
     ukm_service_->ResetClientId();
   }
   // Signal service manager to enable/disable UKM based on new state.
   UpdateRunningServices();
 }
 
 bool ChromeMetricsServiceClient::IsHistorySyncEnabledOnAllProfiles() {
   return SyncDisableObserver::IsHistorySyncEnabledOnAllProfiles();
 }