[telemetry] Add new measurement that counts number of GCs needed to free V8 context.

tools/perf/page_sets/page_reload_cases.py

+# Copyright 2015 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.
+from telemetry.page import page as page_module
+from telemetry.page import page_set as page_set_module
+
+from page_sets import top_pages
+
+
+def _Reload(action_runner):
+  # Numbers below are chosen arbitrarily. For the V8DetachedContextAgeInGC
+  # the number of reloads should be high enough so that V8 could do few
+  # incremeantal GCs.
+  NUMBER_OF_RELOADS = 7
+  WAIT_TIME = 2
+  for _ in xrange(NUMBER_OF_RELOADS):
+    action_runner.ReloadPage()
+    action_runner.Wait(WAIT_TIME)
+
+
+def _CreatePageClassWithReload(page_cls):
+  class DerivedSmoothPage(page_cls):  # pylint: disable=W0232
+
+    def RunPageInteractions(self, action_runner):
+      _Reload(action_runner)
+  return DerivedSmoothPage
+
+
+class PageReloadCasesPageSet(page_set_module.PageSet):
+
+  """ Pages for testing GC efficiency on page reload. """
+
+  def __init__(self):
+    super(PageReloadCasesPageSet, self).__init__(
+        user_agent_type='desktop',
+        archive_data_file='data/top_25.json',
+        bucket=page_set_module.PARTNER_BUCKET)
+
+    self.AddUserStory(_CreatePageClassWithReload(
+        top_pages.GoogleWebSearchPage)(self))
+    self.AddUserStory(_CreatePageClassWithReload(
+        top_pages.GmailPage)(self))
+    self.AddUserStory(_CreatePageClassWithReload(
+        top_pages.GoogleCalendarPage)(self))
+    self.AddUserStory(_CreatePageClassWithReload(
+        top_pages.GoogleDocPage)(self))
+    self.AddUserStory(_CreatePageClassWithReload(
+        top_pages.GooglePlusPage)(self))
+    self.AddUserStory(_CreatePageClassWithReload(
+        top_pages.YoutubePage)(self))
+    self.AddUserStory(_CreatePageClassWithReload(
+        top_pages.WordpressPage)(self))
+    self.AddUserStory(_CreatePageClassWithReload(
+        top_pages.FacebookPage)(self))