Add support for latency measurement to Telemetry smoothness benchmarks.

tools/perf/perf_tools/smoothness_measurement.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 119 matching lines @@
   results.Add('total_tiles_analyzed', 'count',
               totalTilesAnalyzed,
               data_type='unimportant')
   results.Add('solid_color_tiles_analyzed', 'count',
               solidColorTilesAnalyzed,
               data_type='unimportant')
   results.Add('average_tile_analysis_time', 'ms',
               averageAnalysisTimeMS,
               data_type='unimportant')
 
+def CalcLatencyResults(rendering_stats_deltas, results):
+  inputEventCount = rendering_stats_deltas.get(
+      'inputEventCount', 0)
+  totalInputLatencyInSeconds = rendering_stats_deltas.get(
+      'totalInputLatency', 0)
+
+  averageLatency = DivideIfPossibleOrZero(
+      (totalInputLatencyInSeconds * 1000), inputEventCount)
+
+  results.Add('average_latency', 'ms', averageLatency,
+              data_type='unimportant')
+
+
 class SmoothnessMeasurement(page_measurement.PageMeasurement):
   def __init__(self):
     super(SmoothnessMeasurement, 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',
                       action='store_true',
@@ skipping 38 matching lines @@
       load_timings['navigationStart']) / 1000
     results.Add('load_time', 'seconds', load_time_seconds)
     results.Add('dom_content_loaded_time', 'seconds',
                 dom_content_loaded_time_seconds)
 
     CalcFirstPaintTimeResults(results, tab)
     CalcScrollResults(rendering_stats_deltas, results)
     CalcTextureUploadResults(rendering_stats_deltas, results)
     CalcImageDecodingResults(rendering_stats_deltas, results)
     CalcAnalysisResults(rendering_stats_deltas, results)
+    CalcLatencyResults(rendering_stats_deltas, results)
 
     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():
         results.Add(r.name, r.unit, r.value)