Allowing V8ObjectStatsMetric users to specify metrics to capture.

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 144 matching lines @@
     'V8.SizeOf_TYPE_SWITCH_INFO_TYPE'
   ]
 
 class V8ObjectStatsMetric(Metric):
   """V8ObjectStatsMetric gathers statistics on the size of types in the V8 heap.
 
   It does this by enabling the --track_gc_object_stats flag on V8 and reading
   these statistics from the StatsTableMetric.
   """
 
-  def __init__(self):
+  def __init__(self, counters=None):
     super(V8ObjectStatsMetric, self).__init__()
     self._results = None
+    self._counters = counters or _COUNTER_NAMES
 
   @classmethod
   def CustomizeBrowserOptions(cls, options):
     options.AppendExtraBrowserArgs([
         '--enable-stats-table',
         '--enable-benchmarking',
         '--js-flags=--track_gc_object_stats --expose_gc',
         # TODO(rmcilroy): This is needed for --enable-stats-table.  Update once
         # https://codereview.chromium.org/22911027/ lands.
         '--no-sandbox'
     ])
 
   @staticmethod
   def GetV8StatsTable(tab, counters=None):
     counters = counters or _COUNTER_NAMES

[rmcilroy, 2014/01/03 09:58:28]

nit - drop the default argument, and "counters = counters or _COUNTER_NAMES"
line from here please.

 
     return tab.EvaluateJavaScript("""
      (function(counters) {
        var results = {};
        if (!window.chrome || !window.chrome.benchmarking)
         return results;
        try {
         window.gc();  // Trigger GC to ensure stats are checkpointed.
        } catch(e) {
         // window.gc() could have been mapped to something else, just continue.
        }
        for (var i = 0; i < counters.length; i++)
          results[counters[i]] =
              chrome.benchmarking.counterForRenderer(counters[i]);
        return results;
      })(%s);
      """ % json.dumps(counters))
 
   def Start(self, page, tab):
     """Do Nothing."""
     pass
 
   def Stop(self, page, tab):
     """Get the values in the stats table after the page is loaded."""
-    self._results = V8ObjectStatsMetric.GetV8StatsTable(tab)
+    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)