Revise system profile prefs clearing

components/metrics/metrics_log.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 set of user experience metrics data recorded by
 // the MetricsService.  This is the unit of data that is sent to the server.
 
 #ifndef COMPONENTS_METRICS_METRICS_LOG_H_
 #define COMPONENTS_METRICS_METRICS_LOG_H_
 
@@ skipping 69 matching lines @@
   static int64_t GetCurrentTime();
 
   // Records a user-initiated action.
   void RecordUserAction(const std::string& key);
 
   // Record any changes in a given histogram for transmission.
   void RecordHistogramDelta(const std::string& histogram_name,
                             const base::HistogramSamples& snapshot);
 
   // Records the current operating environment, including metrics provided by
-  // the specified set of |metrics_providers|.  Takes the list of installed
-  // plugins, Google Update statistics, and synthetic trial IDs as parameters
-  // because those can't be obtained synchronously from the UI thread.
-  // A synthetic trial is one that is set up dynamically by code in Chrome. For
-  // example, a pref may be mapped to a synthetic trial such that the group
-  // is determined by the pref value.
+  // the specified set of |metrics_providers|.  Takes the list of synthetic
+  // trial IDs as parameters because those can't be obtained synchronously from
+  // the UI thread. A synthetic trial is one that is set up dynamically by code

[Alexei Svitkine (slow), 2016/10/20 16:47:26]

Thanks for removing references to old params.

Actually, the new comment is still not correct because synthetic trial are
generated synchronously on the UI thread. The reason it takes them is because
they're managed by the metrics services.

I suggest just rewording this to not mention the synchronous / UI thread it.
e.g. "Takes a list of synthetic trial IDs as a parameter. A synthetic trial is
one ..."

[manzagop (departed), 2016/10/20 18:38:37]

Done.

+  // in Chrome. For example, a pref may be mapped to a synthetic trial such that
+  // the group is determined by the pref value.
   void RecordEnvironment(
       const std::vector<MetricsProvider*>& metrics_providers,
       const std::vector<variations::ActiveGroupId>& synthetic_trials,
       int64_t install_date,
       int64_t metrics_reporting_enabled_date);
 
   // Loads the environment proto that was saved by the last RecordEnvironment()
   // call from prefs and clears the pref value. On success, returns true and
   // |app_version| contains the recovered version. Otherwise (if there was no
   // saved environment in prefs or it could not be decoded), returns false and
@@ skipping 95 matching lines @@
   const base::TimeTicks creation_time_;
 
   PrefService* local_state_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsLog);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_METRICS_LOG_H_