Add histograms to record the number of writes to the prefs file

base/metrics/statistics_recorder.h

Index: base/metrics/statistics_recorder.h
diff --git a/base/metrics/statistics_recorder.h b/base/metrics/statistics_recorder.h
index 3bef622b76f2f5612be639532bff71cc3b88394d..f60cc924846894808308f163f4d75458c8be85d0 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -33,6 +33,10 @@ class BASE_EXPORT StatisticsRecorder {
   // Initializes the StatisticsRecorder system. Safe to call multiple times.
   static void Initialize();
 
+  // Initializes the StatisticsRecorder system for testing. This will reset all
+  // existing histogram data.
+  static void InitializeForTest();

[Alexei Svitkine (slow), 2015/04/24 16:34:47]

This sounds like Reset rather than initialize. Also, my preferred suffix is
"ForTesting()" - so how about ResetForTesting().

[raymes, 2015/04/27 03:27:54]

Done.

+
   // Find out if histograms can now be registered into our list.
   static bool IsActive();