mac: Expose keychain access frequency to Telemetry.

tools/perf/measurements/__init__.py

+# Copyright 2014 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 sys
+
+from metrics import keychain_metric
+from telemetry.page import page_test
+
+class PageTestMeasurement(page_test.PageTest):

[jeremy, 2014/11/13 11:31:30]

I'd just add the flag and stat as part of the information reported by
StartupMetric, is there a reason that wouldn't work?

[erikchen, 2014/11/13 18:11:09]

I'm not sure that I understand your comment. I thought that we wanted to collect
this stat for all Telemetry tests? Whereas in your suggestion, the stat would
only be collected for Telemetry measurements that use StartupMetric.

+  """Base class for all telemetry measurements based on page_test."""
+
+  def __init__(self, *args, **kwargs):
+    super(PageTestMeasurement, self).__init__(*args, **kwargs)
+    self._in_unit_test = False
+
+  def CustomizeBrowserOptions(self, options):
+    """When subclasses override this method, they must still call this class's
+    implementation.
+    """
+    if sys.platform == 'darwin' and not self._in_unit_test:
+      options.AppendExtraBrowserArgs([
+          '--enable-stats-collection-bindings'

[jeremy, 2014/11/13 11:31:30]

Is there a reason we need to collect this for tests other than the startup
tests?
If so, this flag is already passed in measurements/startup.py

[erikchen, 2014/11/13 22:52:59]

Yes, as per our offline discussion. We will want all telemetry tests on Mac to
check that the keychain isn't accessed more than 10 times.

+      ])
+
+  def ValidateAndMeasurePage(self, page, tab, results):
+    """When subclasses override this method, they must still call this class's
+    implementation.
+    """
+    if sys.platform == 'darwin' and not self._in_unit_test:
+      keychain_metric.KeychainMetric().AddResults(tab, results)
+
+  def SetInUnitTest(self):
+    self._in_unit_test = True