Decouple Metrics Initialization from IO Thread Initialization

components/metrics/data_use_tracker.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_DATA_USE_TRACKER_H_
 #define COMPONENTS_METRICS_DATA_USE_TRACKER_H_
 
 #include <string>
 
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "base/memory/weak_ptr.h"
-#include "base/sequenced_task_runner.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 
 namespace metrics {
 
 typedef base::Callback<void(const std::string&, int, bool)>
     UpdateUsagePrefCallbackType;
 
 // Records the data use of user traffic and UMA traffic in user prefs. Taking
 // into account those prefs it can verify whether certain UMA log upload is
 // allowed.
 class DataUseTracker {
  public:
   explicit DataUseTracker(PrefService* local_state);
   ~DataUseTracker();
 
   // Returns an instance of |DataUseTracker| with provided |local_state| if
   // users data use should be tracked and null pointer otherwise.
   static std::unique_ptr<DataUseTracker> Create(PrefService* local_state);
 
   // Registers data use prefs using provided |registry|.
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
-  // Returns a callback to data use pref updating function. Should be called on
-  // UI thread.
-  UpdateUsagePrefCallbackType GetDataUseForwardingCallback(
-      scoped_refptr<base::SequencedTaskRunner> ui_task_runner);
+  // Updates data usage prefs according to what the PrefService expects.

[Alexei Svitkine (slow), 2016/11/30 19:16:27]

"according to what the PrefService expects" doesn't make very much sense to me.

How about:

// Updates data usage tracking prefs with the specified values.

Also change the header comment on the MetricsService function likewise.

[robliao, 2016/11/30 20:33:13]

Done.

+  void UpdateMetricsUsagePrefs(
+      const std::string& service_name, int message_size, bool is_cellular);
 
   // Returns whether a log with provided |log_bytes| can be uploaded according
   // to data use ratio and UMA quota provided by variations.
   bool ShouldUploadLogOnCellular(int log_bytes);
 
  private:
   FRIEND_TEST_ALL_PREFIXES(DataUseTrackerTest, CheckUpdateUsagePref);
   FRIEND_TEST_ALL_PREFIXES(DataUseTrackerTest, CheckRemoveExpiredEntries);
   FRIEND_TEST_ALL_PREFIXES(DataUseTrackerTest, CheckComputeTotalDataUse);
   FRIEND_TEST_ALL_PREFIXES(DataUseTrackerTest, CheckCanUploadUMALog);
 
-  // Updates data usage prefs on UI thread according to what Prefservice
-  // expects.
-  void UpdateMetricsUsagePrefsOnUIThread(const std::string& service_name,
-                                         int message_size,
-                                         bool is_cellular);
 

[Alexei Svitkine (slow), 2016/11/30 19:16:27]

Nit: Remove extra line.

[robliao, 2016/11/30 20:33:13]

Done.

   // Updates provided |pref_name| for a current date with the given message
   // size.
   void UpdateUsagePref(const std::string& pref_name, int message_size);
 
   // Removes entries from the all data use  prefs.
   void RemoveExpiredEntries();
 
   // Removes entries from the given |pref_name| if they are more than 7 days
   // old.
   void RemoveExpiredEntriesForPref(const std::string& pref_name);
@@ skipping 11 matching lines @@
   // Returns the current date for measurement.
   virtual base::Time GetCurrentMeasurementDate() const;
 
   // Returns the current date as a string with a proper formatting.
   virtual std::string GetCurrentMeasurementDateAsString() const;
 
   PrefService* local_state_;
 
   base::ThreadChecker thread_checker_;
 
-  base::WeakPtrFactory<DataUseTracker> weak_ptr_factory_;
-
   DISALLOW_COPY_AND_ASSIGN(DataUseTracker);
 };
 
 }  // namespace metrics
 #endif  // COMPONENTS_METRICS_DATA_USE_TRACKER_H_