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

components/browser_watcher/watcher_metrics_provider_win.h

 // Copyright (c) 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.
 
 #ifndef COMPONENTS_BROWSER_WATCHER_WATCHER_METRICS_PROVIDER_WIN_H_
 #define COMPONENTS_BROWSER_WATCHER_WATCHER_METRICS_PROVIDER_WIN_H_
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/strings/string16.h"
 #include "base/task_runner.h"
-#include "base/threading/thread_checker.h"
 #include "components/metrics/metrics_provider.h"
 
 namespace browser_watcher {
 
 // Provides stability data captured by the Chrome Watcher, namely the browser
 // process exit codes.
 class WatcherMetricsProviderWin : public metrics::MetricsProvider {
  public:
   // A callback that provides product name, version number and channel name.
   using GetExecutableDetailsCallback =
       base::Callback<void(base::string16*, base::string16*, base::string16*)>;
 
   static const char kBrowserExitCodeHistogramName[];
 
-  // Initializes the reporter. |io_task_runner| is used for collecting
-  // postmortem reports and clearing leftover data in registry if metrics
-  // reporting is disabled.
+  // Initializes the reporter.
   WatcherMetricsProviderWin(const base::string16& registry_path,
                             const base::FilePath& user_data_dir,
                             const base::FilePath& crash_dir,
-                            const GetExecutableDetailsCallback& exe_details_cb,
-                            base::TaskRunner* io_task_runner);
+                            const GetExecutableDetailsCallback& exe_details_cb);
   ~WatcherMetricsProviderWin() override;
 
   // metrics::MetricsProvider implementation.
   void OnRecordingEnabled() override;
   void OnRecordingDisabled() override;
   // Note: this function collects metrics, some of which are related to the
   // previous run's version and some to the current version. Doing the correct
   // attribution on upgrade is difficult, and currently ignored. Metrics
   // clearing is one mechanism to avoid misattribution, but is not used in this
   // case (ClearSavedStabilityMetrics is not overridden) as version
   // misattribution is preferred to data loss. Metrics will likely be attributed
   // to the previous run's version, unless no initial log is sent, in which case
   // they should be attributed to the current version (though they may actually
   // be attributed to still another following version).
   // TODO(manzagop): proper metric version attribution on upgrade.
   void ProvideStabilityMetrics(
       metrics::SystemProfileProto* system_profile_proto) override;
 
   // Collects postmortem reports asynchronously and calls |done_callback| when
   // done.
   void CollectPostmortemReports(const base::Closure& done_callback);
 
  private:
   // TODO(manzagop): avoid collecting reports for clean exits from the fast exit
   // path.
-  void CollectPostmortemReportsOnBlockingPool();
+  void CollectPostmortemReportsImpl();
 
   bool recording_enabled_;
   bool cleanup_scheduled_;
   const base::string16 registry_path_;
   const base::FilePath user_data_dir_;
   const base::FilePath crash_dir_;
   GetExecutableDetailsCallback exe_details_cb_;
-  scoped_refptr<base::TaskRunner> io_task_runner_;
+
+  // Used for collecting postmortem reports and clearing leftover data in
+  // registry if metrics reporting is disabled.
+  scoped_refptr<base::TaskRunner> task_runner_;
+
   base::WeakPtrFactory<WatcherMetricsProviderWin> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WatcherMetricsProviderWin);
 };
 
 }  // namespace browser_watcher
 
 #endif  // COMPONENTS_BROWSER_WATCHER_WATCHER_METRICS_PROVIDER_WIN_H_