Revise system profile prefs clearing

components/metrics/metrics_log.h

Index: components/metrics/metrics_log.h
diff --git a/components/metrics/metrics_log.h b/components/metrics/metrics_log.h
index 6b37e7b4c9805ae535c014939703e965a791f397..78fc4f0bd22e5cc0301df611b3b8236e057407d6 100644
--- a/components/metrics/metrics_log.h
+++ b/components/metrics/metrics_log.h
@@ -87,12 +87,11 @@ class MetricsLog {
                             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,