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

components/metrics/file_metrics_provider.h

 // Copyright 2016 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_METRICS_FILE_METRICS_PROVIDER_H_
 #define COMPONENTS_METRICS_FILE_METRICS_PROVIDER_H_
 
 #include <list>
 #include <memory>
 #include <string>
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/weak_ptr.h"
 #include "base/metrics/statistics_recorder.h"
-#include "base/threading/thread_checker.h"
+#include "base/sequence_checker.h"
 #include "base/time/time.h"
 #include "components/metrics/metrics_provider.h"
 
 class PrefRegistrySimple;
 class PrefService;
 
 namespace base {
 class TaskRunner;
 }
 
@@ skipping 62 matching lines @@
     ASSOCIATE_INTERNAL_PROFILE,
 
     // Like above but fall back to ASSOCIATE_PREVIOUS_RUN if there is no
     // embedded profile. This has a small cost during startup as that is
     // when previous-run metrics are sent so the file has be checked at
     // that time even though actual transfer will be delayed if an
     // embedded profile is found.
     ASSOCIATE_INTERNAL_PROFILE_OR_PREVIOUS_RUN,
   };
 
-  FileMetricsProvider(const scoped_refptr<base::TaskRunner>& task_runner,
-                      PrefService* local_state);
+  explicit FileMetricsProvider(PrefService* local_state);
   ~FileMetricsProvider() override;
 
   // Indicates a file or directory to be monitored and how the file or files
   // within that directory are used. Because some metadata may need to persist
   // across process restarts, preferences entries are used based on the
   // |prefs_key| name. Call RegisterPrefs() with the same name to create the
   // necessary keys in advance. Set |prefs_key| empty (nullptr will work) if
   // no persistence is required. ACTIVE files shouldn't have a pref key as
   // they update internal state about what has been previously sent.
   void RegisterSource(const base::FilePath& path,
                       SourceType type,
                       SourceAssociation source_association,
                       const base::StringPiece prefs_key);
 
   // Registers all necessary preferences for maintaining persistent state
   // about a monitored file across process restarts. The |prefs_key| is
   // typically the filename.
   static void RegisterPrefs(PrefRegistrySimple* prefs,
                             const base::StringPiece prefs_key);
 
+  // Sets the task runner to use for testing.
+  static void SetTaskRunnerForTesting(
+      const scoped_refptr<base::TaskRunner>& task_runner);
+
  private:
   friend class FileMetricsProviderTest;
 
   // The different results that can occur accessing a file.
   enum AccessResult {
     // File was successfully mapped.
     ACCESS_RESULT_SUCCESS,
 
     // File does not exist.
     ACCESS_RESULT_DOESNT_EXIST,
@@ skipping 86 matching lines @@
   SourceInfoList sources_with_profile_;
 
   // A list of sources for a previous run. These are held separately because
   // they are not subject to the periodic background checking that handles
   // metrics for the current run.
   SourceInfoList sources_for_previous_run_;
 
   // The preferences-service used to store persistent state about sources.
   PrefService* pref_service_;
 
-  base::ThreadChecker thread_checker_;
+  SEQUENCE_CHECKER(sequence_checker_);
   base::WeakPtrFactory<FileMetricsProvider> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FileMetricsProvider);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_FILE_METRICS_PROVIDER_H_