[Telemetry] Add support for capturing V8 object stats to Telemetry.

tools/perf/measurements/page_cycler.py

 # Copyright (c) 2012 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.
 
 """The page cycler measurement.
 
 This measurement registers a window load handler in which is forces a layout and
 then records the value of performance.now(). This call to now() measures the
 time from navigationStart (immediately after the previous page's beforeunload
 event) until after the layout in the page's load event. In addition, two garbage
 collections are performed in between the page loads (in the beforeunload event).
 This extra garbage collection time is not included in the measurement times.
 
 Finally, various memory and IO statistics are gathered at the very end of
 cycling all pages.
 """
 
 import os
 import sys
 
 from metrics import io
 from metrics import memory
+from metrics import v8_object_stats
 from telemetry.core import util
 from telemetry.page import page_measurement
 
 class PageCycler(page_measurement.PageMeasurement):
   def __init__(self, *args, **kwargs):
     super(PageCycler, self).__init__(*args, **kwargs)
 
     with open(os.path.join(os.path.dirname(__file__),
                            'page_cycler.js'), 'r') as f:
       self._page_cycler_js = f.read()
 
+    self._record_v8_object_stats = False
+
     self._memory_metric = None
+    self._v8_object_stats_metric = None
+
 
   def AddCommandLineOptions(self, parser):
     # The page cyclers should default to 10 iterations. In order to change the
     # default of an option, we must remove and re-add it.
     # TODO: Remove this after transition to run_benchmark.
     pageset_repeat_option = parser.get_option('--pageset-repeat')
     pageset_repeat_option.default = 10
     parser.remove_option('--pageset-repeat')
     parser.add_option(pageset_repeat_option)
 
+    parser.add_option('--v8-object-stats',
+        action='store_true',
+        help='Enable detailed V8 object statistics.')
+
   def DidStartBrowser(self, browser):
     """Initialize metrics once right after the browser has been launched."""
     self._memory_metric = memory.MemoryMetric(browser)
+    if self._record_v8_object_stats:
+      self._v8_object_stats_metric = v8_object_stats.V8ObjectStatsMetric()
 
   def DidStartHTTPServer(self, tab):
     # Avoid paying for a cross-renderer navigation on the first page on legacy
     # page cyclers which use the filesystem.
     tab.Navigate(tab.browser.http_server.UrlOf('nonexistent.html'))
 
   def WillNavigateToPage(self, page, tab):
     page.script_to_evaluate_on_commit = self._page_cycler_js
 
   def DidNavigateToPage(self, page, tab):
     self._memory_metric.Start(page, tab)
+    if self._record_v8_object_stats:
+      self._v8_object_stats_metric.Start(page, tab)
 
   def CustomizeBrowserOptions(self, options):
-    memory.MemoryMetric.CustomizeBrowserOptions(options)
-    io.IOMetric.CustomizeBrowserOptions(options)
+    options.AppendExtraBrowserArg('--enable-stats-collection-bindings')
     options.AppendExtraBrowserArg('--js-flags=--expose_gc')
+    options.AppendExtraBrowserArg('--no-sandbox')
+
+    # Old commandline flags used for reference builds.
+    options.AppendExtraBrowserArg('--dom-automation')
+
+    # Add custom options required by metrics
+    if options.v8_object_stats:
+      self._record_v8_object_stats = True
+      v8_object_stats.V8ObjectStatsMetric.CustomizeBrowserOptions(options)
 
     # Temporarily disable typical_25 page set on mac.
     if sys.platform == 'darwin' and sys.argv[-1].endswith('/typical_25.json'):
       print 'typical_25 is currently disabled on mac. Skipping test.'
       sys.exit(0)
 
   def MeasurePage(self, page, tab, results):
     def _IsDone():
       return bool(tab.EvaluateJavaScript('__pc_load_time'))
     util.WaitFor(_IsDone, 60)
     results.Add('page_load_time', 'ms',
                 int(float(tab.EvaluateJavaScript('__pc_load_time'))),
                 chart_name='times')
 
     self._memory_metric.Stop(page, tab)
     self._memory_metric.AddResults(tab, results)
+    if self._record_v8_object_stats:
+      self._v8_object_stats_metric.Stop(page, tab)
+      self._v8_object_stats_metric.AddResults(tab, results)
 
   def DidRunTest(self, tab, results):
     self._memory_metric.AddSummaryResults(results)
     io.IOMetric().AddSummaryResults(tab, results)