[Telemetry]: Fix v8_object_stats metric to avoid having a '.' in trace names

tools/perf/metrics/v8_object_stats.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import json
 import logging
 
 from metrics import Metric
 
 _COUNTER_NAMES = [
@@ skipping 194 matching lines @@
   def Stop(self, page, tab):
     """Get the values in the stats table after the page is loaded."""
     self._results = V8ObjectStatsMetric.GetV8StatsTable(tab, self._counters)
     if not self._results:
       logging.warning('No V8 object stats from website: ' + page.display_name)
 
   def AddResults(self, tab, results):
     """Add results for this page to the results object."""
     assert self._results != None, 'Must call Stop() first'
     for counter_name in self._results:
-      results.Add(counter_name, 'kb', self._results[counter_name] / 1024.0)
+      display_name = counter_name.replace('.', '_')
+      results.Add(display_name, 'kb', self._results[counter_name] / 1024.0)