[Telemetry] Power metric: subtract quiescent power draw from result

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
 # pylint: disable=W0401,W0614
@@ skipping 44 matching lines @@
   def testSyntheticDelayConfiguration(self):
     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)
 
     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 50 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)