Added support for improvement_direction to relevant values, which is propogated to chartjson.

tools/perf/benchmarks/service_worker.py

Index: tools/perf/benchmarks/service_worker.py
diff --git a/tools/perf/benchmarks/service_worker.py b/tools/perf/benchmarks/service_worker.py
index 6fbdc10977ac3bcd3e5940734ba5d22c0d6c3337..d7fd19221cec6cb802eaa472d33161bb172d5089 100644
--- a/tools/perf/benchmarks/service_worker.py
+++ b/tools/perf/benchmarks/service_worker.py
@@ -13,6 +13,7 @@ from telemetry.core import util
 from telemetry.page import page_test
 from telemetry.timeline import async_slice as async_slice_module
 from telemetry.timeline import slice as slice_module
+from telemetry.value import improvement_direction
 from telemetry.value import scalar
 
 
@@ -29,10 +30,12 @@ class _ServiceWorkerTimelineMetric(object):
       sanitized_counter_name = counter_name.replace('.', '_')
 
       results.AddValue(scalar.ScalarValue(
-          results.current_page, sanitized_counter_name, 'count', total))
+          results.current_page, sanitized_counter_name, 'count', total,
+          improvement_direction=improvement_direction.DOWN))
       results.AddValue(scalar.ScalarValue(
           results.current_page, sanitized_counter_name + '_avg', 'count',
-          total / float(len(counter.totals))))
+          total / float(len(counter.totals)),
+          improvement_direction=improvement_direction.DOWN))
 
   def AddResultsOfEvents(
       self, process, thread_regex_string, event_regex_string, results):
@@ -75,11 +78,14 @@ class _ServiceWorkerTimelineMetric(object):
 
     full_name = thread_name + '|' + sanitized_event_name
     results.AddValue(scalar.ScalarValue(
-        results.current_page, full_name, 'ms', total))
+        results.current_page, full_name, 'ms', total,
+        improvement_direction=improvement_direction.DOWN))
     results.AddValue(scalar.ScalarValue(
-        results.current_page, full_name + '_max', 'ms', biggest_jank))
+        results.current_page, full_name + '_max', 'ms', biggest_jank,
+        improvement_direction=improvement_direction.DOWN))
     results.AddValue(scalar.ScalarValue(
-        results.current_page, full_name + '_avg', 'ms', total / len(times)))
+        results.current_page, full_name + '_avg', 'ms', total / len(times),
+        improvement_direction=improvement_direction.DOWN))
 
 
 class _ServiceWorkerMeasurement(page_test.PageTest):
@@ -160,7 +166,8 @@ class _ServiceWorkerMicroBenchmarkMeasurement(page_test.PageTest):
     json = tab.EvaluateJavaScript('window.results || {}')
     for key, value in json.iteritems():
       results.AddValue(scalar.ScalarValue(
-          results.current_page, key, value['units'], value['value']))
+          results.current_page, key, value['units'], value['value'],
+          improvement_direction=improvement_direction.DOWN))
 
     # Retrieve TRACE_EVENTs
     timeline_metric = _ServiceWorkerTimelineMetric()