[Telemetry] Report stddev for JetStream.

tools/perf/benchmarks/jetstream.py

 # Copyright 2014 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.
 
 """Runs Apple's JetStream benchmark.
 
 JetStream combines a variety of JavaScript benchmarks, covering a variety of
 advanced workloads and programming techniques, and reports a single score that
 balances them using geometric mean.
 
 Each benchmark measures a distinct workload, and no single optimization
 technique is sufficient to speed up all benchmarks. Latency tests measure that
 a web application can start up quickly, ramp up to peak performance quickly,
 and run smoothly without interruptions. Throughput tests measure the sustained
 peak performance of a web application, ignoring ramp-up time and spikes in
 smoothness. Some benchmarks demonstrate tradeoffs, and aggressive or
 specialized optimization for one benchmark might make another benchmark slower.
 """
 
 import json
 import os
 
 from telemetry import benchmark
 from telemetry.page import page_set
 from telemetry.page import page_test
 from telemetry.util import statistics
 from telemetry.value import list_of_scalar_values
-from telemetry.value import scalar
 
 
 class _JetstreamMeasurement(page_test.PageTest):
   def __init__(self):
     super(_JetstreamMeasurement, self).__init__()
 
   def WillNavigateToPage(self, page, tab):
     page.script_to_evaluate_on_commit = """
         var __results = [];
         var __real_log = window.console.log;
@@ skipping 13 matching lines @@
         })();
         """
 
     tab.WaitForDocumentReadyStateToBeComplete()
     tab.EvaluateJavaScript('JetStream.start()')
     tab.WaitForJavaScriptExpression(get_results_js, 600)
 
     result = tab.EvaluateJavaScript(get_results_js)
     result = json.loads(result.partition(': ')[2])
 
-    all_scores = []
+    all_score_lists = []
     for k, v in result.iteritems():
       results.AddValue(list_of_scalar_values.ListOfScalarValues(
           results.current_page, k.replace('.', '_'), 'score', v['result'],
           important=False))
       # Collect all test scores to compute geometric mean.
-      all_scores.extend(v['result'])
-    total = statistics.GeometricMean(all_scores)
-    results.AddSummaryValue(
-        scalar.ScalarValue(None, 'Score', 'score', total))
+      for i, score in enumerate(v['result']):
+        if len(all_score_lists) <= i:
+          all_score_lists.append([])
+        all_score_lists[i].append(score)
+    all_scores = []
+    for score_list in all_score_lists:
+      all_scores.append(statistics.GeometricMean(score_list))
+    results.AddSummaryValue(list_of_scalar_values.ListOfScalarValues(
+        None, 'Score', 'score', all_scores))
 
 
 @benchmark.Disabled('android', 'xp')  # crbug.com/381742
 class Jetstream(benchmark.Benchmark):
   test = _JetstreamMeasurement
 
   def CreatePageSet(self, options):
     ps = page_set.PageSet(
         archive_data_file='../page_sets/data/jetstream.json',
         make_javascript_deterministic=False,
         file_path=os.path.abspath(__file__))
     ps.AddPageWithDefaultRunNavigate('http://browserbench.org/JetStream/')
     return ps