Persist setup metrics and have Chrome report them during UMA upload.

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 32f381bd717ba82b5a66b995e7beda326f42e402..9033419e5a9a809f82cdde666c31836db870d611 100644
--- a/base/metrics/statistics_recorder.h
+++ b/base/metrics/statistics_recorder.h
@@ -133,6 +133,11 @@ class BASE_EXPORT StatisticsRecorder {
   // state that allows a new initialization.
   static void ResetForTesting();
 
+  // Removes a histogram from the internal set of known ones. This can be
+  // necessary during testing persistent histograms where the underlying
+  // memory is being released.
+  static void ForgetHistogramForTesting(const std::string& name);
+
  private:
   // We keep a map of callbacks to histograms, so that as histograms are
   // created, we can set the callback properly.