Telemetry: Initialize smoothness and thread_times metrics before page load, not after.

tools/perf/measurements/smoothness_unittest.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 sys
 
 from measurements import smoothness
 from telemetry.core import wpr_modes
 from telemetry.page import page
 from telemetry.page import page_measurement_unittest_base
 from telemetry.unittest import options_for_unittests
@@ skipping 43 matching lines @@
     test_page = page.Page('http://dummy', None)
     test_page.synthetic_delays = {
         'cc.BeginMainFrame': { 'target_duration': 0.012 },
         'cc.DrawAndSwap': { 'target_duration': 0.012, 'mode': 'alternating' },
         'gpu.PresentingFrame': { 'target_duration': 0.012 }
     }
 
     tab = FakeTab()
     measurement = smoothness.Smoothness()
     measurement.WillStartBrowser(tab.browser)
-    measurement.WillRunActions(test_page, tab)
+    measurement.WillNavigateToPage(test_page, tab)

[picksi, 2014/07/18 11:30:58]

Are we just moving this problem to somewhere else for a future developer to run
into? Is there other work being done in WillRunActions that we are now failing
to do (or will fail to do in the future as the code grows)? I can't think of an
easy solution here, as we are relying on an unexpected side effect of a function
(i.e. starting the metric stuff)... :)

[Dominik Grewe, 2014/07/18 16:10:51]

How about we call both? :) That's what's happening inside Telemetry and it means
we don't need to know what happens when. (And I need it for the test to pass in
my new patch set...)

[picksi, 2014/07/18 16:47:20]

Can it safely be doubly initialized without losing the data recorded between 1st
init and 2nd init?

Would it be too big and scary to make the whole thing lazily initialize, so it
gets initialized the first time it is used? Is there some sort of singleton at
the bottom of this?

 
     expected_category_filter = [
         'DELAY(cc.BeginMainFrame;0.012000;static)',
         'DELAY(cc.DrawAndSwap;0.012000;alternating)',
         'DELAY(gpu.PresentingFrame;0.012000;static)',
         'benchmark'
     ]
     actual_category_filter = tab.browser.category_filter.split(',')
     actual_category_filter.sort()
 
@@ skipping 49 matching lines @@
     measurement = smoothness.Smoothness()
     results = self.RunMeasurement(measurement, ps, options=self._options)
     self.assertEquals(0, len(results.failures))
 
     mostly_smooth = results.FindAllPageSpecificValuesNamed('mostly_smooth')
     self.assertEquals(len(mostly_smooth), 1)
     self.assertGreaterEqual(mostly_smooth[0].GetRepresentativeNumber(), 0)
 
   def testCleanUpTrace(self):
     self.TestTracingCleanedUp(smoothness.Smoothness, self._options)