When specifying a new create histogram callback, reset all histograms so they recreate themselves o…

src/v8-counters.h

Index: src/v8-counters.h
diff --git a/src/v8-counters.h b/src/v8-counters.h
index e230613a72067089b53240246c94fd46029d6783..4a5755c3e6bd1c03e3b22bec6c2b20702de5b08e 100644
--- a/src/v8-counters.h
+++ b/src/v8-counters.h
@@ -363,6 +363,8 @@ class Counters {
     return &state_counters_[state];
   }
 
+  void ResetHistograms();
+
  private:
 #define HT(name, caption) \
   HistogramTimer name##_;