Serialize Histograms more efficiently.

tracing/tracing/value/ui/value_set_table.html

Index: tracing/tracing/value/ui/value_set_table.html
diff --git a/tracing/tracing/value/ui/value_set_table.html b/tracing/tracing/value/ui/value_set_table.html
index 9fcbeaa3f7e8f493af6731d527c9441f568b0374..aa3e9a400790c9c263fe1db6846abbcd750445b1 100644
--- a/tracing/tracing/value/ui/value_set_table.html
+++ b/tracing/tracing/value/ui/value_set_table.html
@@ -687,9 +687,7 @@ tr.exportTo('tr.ui', function() {
               // TODO(eakuefner) When MergedFrom diagnostic lands, only create a
               // new Histogram if |row.columns[name]| doesn't have it so that we
               // don't create new Histograms unnecessarily.
-              var merged = new tr.v.Histogram(value.name, value.unit,
-                  tr.v.HistogramBinBoundaries.createWithBoundaries(
-                      value.binBoundaries));
+              var merged = value.cloneEmpty();
               merged.addHistogram(row.columns[name]);
               merged.addHistogram(value);
               row.columns[name] = merged;