[Telemetry] Measure power in tab_switching measurement

tools/perf/metrics/speedindex.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 collections
 import os
 
 from metrics import Metric
 from telemetry.core import bitmap
 
@@ skipping 60 matching lines @@
     A page may repeatedly request resources in an infinite loop; a timeout
     should be placed in any measurement that uses this metric, e.g.:
       def IsDone():
         return self._speedindex.IsFinished(tab)
       util.WaitFor(IsDone, 60)
 
     Returns:
       True if 2 seconds have passed since last resource received, false
       otherwise.
     """
-    if self._is_finished:
-      return True
-
-    # The script that provides the function window.timeSinceLastResponseMs()
-    # needs to be loaded for this function, but it must be loaded AFTER
-    # the Start method is called, because if the Start method is called in
-    # the PageMeasurement's WillNavigateToPage function, then it will
-    # not be available here. The script should only be re-loaded once per page
-    # so that variables in the script get reset only for a new page.
-    if not self._script_is_loaded:
-      tab.ExecuteJavaScript(self._js)
-      self._script_is_loaded = True
-
-    time_since_last_response_ms = tab.EvaluateJavaScript(
-        "window.timeSinceLastResponseAfterLoadMs()")
-    self._is_finished = time_since_last_response_ms > 2000
-    return self._is_finished
+    return tab.HasReachedQuiescence()
 
 
 class SpeedIndexImpl(object):
 
   def Start(self, tab):
     raise NotImplementedError()
 
   def Stop(self, tab):
     raise NotImplementedError()
 
@@ skipping 210 matching lines @@
     frame = paint_event.args['frameId']
     return (frame,) + GetBox(paint_event.args['data']['clip'])
 
   def _GroupEventByRectangle(self, paint_events):
     """Group all paint events according to the rectangle that they update."""
     result = collections.defaultdict(list)
     for event in paint_events:
       assert event.name == 'Paint'
       result[self._GetRectangle(event)].append(event)
     return result