Add UMA/Telemetry stats for end-to-end scroll latency

tools/perf/measurements/smoothness.py

 # Copyright (c) 2012 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 perf_tools import smoothness_metrics
 from telemetry.core import util
 from telemetry.page import page_measurement
 
 class DidNotScrollException(page_measurement.MeasurementFailure):
   def __init__(self):
     super(DidNotScrollException, self).__init__('Page did not scroll')
@@ skipping 141 matching lines @@
 
 def CalcLatencyResults(rendering_stats_deltas, results):
   CalcLatency(rendering_stats_deltas, 'inputEventCount', 'totalInputLatency',
               'average_latency', results)
   CalcLatency(rendering_stats_deltas, 'touchUICount', 'totalTouchUILatency',
               'average_touch_ui_latency', results)
   CalcLatency(rendering_stats_deltas, 'touchAckedCount',
               'totalTouchAckedLatency',
               'average_touch_acked_latency',
               results)
+  CalcLatency(rendering_stats_deltas, 'scrollUpdateCount',
+              'totalScrollUpdateLatency',
+              'average_scroll_update_latency', results)
 
 class Smoothness(page_measurement.PageMeasurement):
   def __init__(self):
     super(Smoothness, self).__init__('smoothness')
     self.force_enable_threaded_compositing = False
     self.use_gpu_benchmarking_extension = True
     self._metrics = None
 
   def AddCommandLineOptions(self, parser):
     parser.add_option('--report-all-results', dest='report_all_results',
@@ skipping 50 matching lines @@
 
     if self.options.report_all_results:
       for k, v in rendering_stats_deltas.iteritems():
         results.Add(k, '', v)
 
     if tab.browser.platform.IsRawDisplayFrameRateSupported():
       for r in tab.browser.platform.GetRawDisplayFrameRateMeasurements():
         if r.value is None:
           raise MissingDisplayFrameRate(r.name)
         results.Add(r.name, r.unit, r.value)