Stats tree seems to work properly, including pruning of "empty" leaves
diff --git a/utils/load-stats.h b/utils/load-stats.h
index 8b2433e..a9f2e5f 100644
--- a/utils/load-stats.h
+++ b/utils/load-stats.h
@@ -53,7 +53,7 @@
   GetStats () const;
 
   bool
-  IsEmpty () const;
+  IsZero () const;
   
 private:
   uint32_t counter_;
@@ -61,6 +61,9 @@
   double avg1_;
   double avg5_;
   double avg15_;
+
+  friend std::ostream &
+  operator << (std::ostream &os, const LoadStats &stats);
 };
 
 std::ostream &