Create and display "comparison statistics" to compare two statistics

tools/telemetry/telemetry/page/buildbot_page_measurement_results.py

Index: tools/telemetry/telemetry/page/buildbot_page_measurement_results.py
diff --git a/tools/telemetry/telemetry/page/buildbot_page_measurement_results.py b/tools/telemetry/telemetry/page/buildbot_page_measurement_results.py
index 73a58aa732cd7d19a63e52be220fe35b6abbd9cf..53da5cb2054327c34e736168692f19812083afd7 100644
--- a/tools/telemetry/telemetry/page/buildbot_page_measurement_results.py
+++ b/tools/telemetry/telemetry/page/buildbot_page_measurement_results.py
@@ -6,6 +6,7 @@ from collections import defaultdict
 from itertools import chain
 
 from telemetry.page import page_measurement_results
+from telemetry.page import page_measurement_value
 from telemetry.page import perf_tests_helper
 
 class BuildbotPageMeasurementResults(
@@ -69,11 +70,14 @@ class BuildbotPageMeasurementResults(
         by_name_data_type = 'unimportant-histogram'
       else:
         by_name_data_type = 'unimportant'
-      if '.' in measurement and 'histogram' not in data_type:
-        measurement, trace = measurement.split('.', 1)
-        trace += self._trace_tag
-      else:
-        trace = measurement + self._trace_tag
+
+      trace = ''
+      if 'histogram' not in data_type:
+        measurement, trace = \
+            page_measurement_value.ChartTraceFromMeasurement(measurement)
+      if not measurement:
+        measurement = trace
+      trace += self._trace_tag
 
       # Print individual _by_name results if there's more than 1 successful
       # page, or if there's exactly 1 successful page but a failure exists.
@@ -106,6 +110,30 @@ class BuildbotPageMeasurementResults(
             values = list(chain.from_iterable(values))
           self._PrintPerfResult(measurement, trace, values, units, data_type)
 
+    # Output all the by_name comparisons.  This is safe no matter
+    # whether the _by_name results above were output, as the final
+    # display needs to detect and ignore comparisons that refer to
+    # non-existent base statistics.
+    for compare_stat in [x for x in self._comparison_stats.iteritems()]:
+      (result_stat_measurement, result_stat_trace) = \
+          page_measurement_value.ChartTraceFromMeasurement(compare_stat[0])
+      if not result_stat_measurement:
+        result_stat_measurement = result_stat_trace
+      (ref_stat_measurement, ref_stat_trace) = \
+          page_measurement_value.ChartTraceFromMeasurement(
+        compare_stat[1]['reference'])
+      if not ref_stat_measurement:
+        ref_stat_measurement = ref_stat_trace
+      (comparison_stat_measurement, comparison_stat_trace) = \
+          page_measurement_value.ChartTraceFromMeasurement(
+        compare_stat[1]['comparison'])
+      if not comparison_stat_measurement:
+        comparison_stat_measurement = comparison_stat_trace
+      for name in unique_pages:
+        self.AddComparison(name, ref_stat_measurement + '_by_url',
+                           name, comparison_stat_measurement + '_by_url',
+                           name, result_stat_measurement + '_by_url')
+
     # If there were no failed pages, output the overall results (results not
     # associated with a page).
     if not (self.errors or self.failures):