Resetting metrics ids on clump detection.

chrome/browser/metrics/metrics_service.h

Index: chrome/browser/metrics/metrics_service.h
diff --git a/chrome/browser/metrics/metrics_service.h b/chrome/browser/metrics/metrics_service.h
index f50934d0db5d53e72d624dcde35a735a02e18a23..15c66d72ed857936968e401670b2f2d58d74f12e 100644
--- a/chrome/browser/metrics/metrics_service.h
+++ b/chrome/browser/metrics/metrics_service.h
@@ -368,6 +368,10 @@ class MetricsService
                   base::TimeDelta* incremental_uptime,
                   base::TimeDelta* uptime);
 
+  // Reset the client id and low entropy source if the kMetricsResetMetricIDs
+  // pref is true.
+  void ResetMetricsIDsIfNecessary();
+
   // Returns the low entropy source for this client. This is a random value
   // that is non-identifying amongst browser clients. This method will
   // generate the entropy source value if it has not been called before.
@@ -523,6 +527,11 @@ class MetricsService
 
   content::NotificationRegistrar registrar_;
 
+  // Set to true when the client id and low entropy source have been reset due
+  // to the kMetricsResetIds pref being true. This prevents multiple resets

[Alexei Svitkine (slow), 2014/03/28 19:49:02]

This comment isn't correct. It's also set to true if the check was performed and
nothing was reset.

[jwd, 2014/03/28 19:58:58]

Done.

+  // within the same chrome session.
+  bool metrics_ids_reset_check_performed_;
+
   // Indicate whether recording and reporting are currently happening.
   // These should not be set directly, but by calling SetRecording and
   // SetReporting.
@@ -639,6 +648,7 @@ class MetricsService
   FRIEND_TEST_ALL_PREFIXES(MetricsServiceTest,
                            PermutedEntropyCacheClearedWhenLowEntropyReset);
   FRIEND_TEST_ALL_PREFIXES(MetricsServiceTest, RegisterSyntheticTrial);
+  FRIEND_TEST_ALL_PREFIXES(MetricsServiceTest, ResetMetricsIDs);
   FRIEND_TEST_ALL_PREFIXES(MetricsServiceBrowserTest,
                            CheckLowEntropySourceUsed);
   FRIEND_TEST_ALL_PREFIXES(MetricsServiceReportingTest,