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

tools/perf/measurements/oilpan_gc_times.py

Index: tools/perf/measurements/oilpan_gc_times.py
diff --git a/tools/perf/measurements/oilpan_gc_times.py b/tools/perf/measurements/oilpan_gc_times.py
index b642b486afce2a729139bb72e6a13b00a2d8d71c..6d818e32e562a49ab4d186bbf1a34588019f11de 100644
--- a/tools/perf/measurements/oilpan_gc_times.py
+++ b/tools/perf/measurements/oilpan_gc_times.py
@@ -65,11 +65,12 @@ def _AddTracingResults(events, results):
   for name in _NAMES_TO_DUMP:
     if values[name]:
       results.AddValue(list_of_scalar_values.ListOfScalarValues(
-          page, name, unit, values[name]))
+          page, name, unit, values[name], higher_is_better=False))
       results.AddValue(scalar.ScalarValue(
-          page, name + '_max', unit, max(values[name])))
+          page, name + '_max', unit, max(values[name]),
+          higher_is_better=False))
     results.AddValue(scalar.ScalarValue(
-        page, name + '_total', unit, sum(values[name])))
+        page, name + '_total', unit, sum(values[name]), higher_is_better=False))
 
   for do_type in ['mark', 'sweep']:
     work_time = 0
@@ -81,7 +82,8 @@ def _AddTracingResults(events, results):
   gc_time = 0
   for key in values:
     gc_time += sum(values[key])
-  results.AddValue(scalar.ScalarValue(page, 'oilpan_gc', unit, gc_time))
+  results.AddValue(scalar.ScalarValue(page, 'oilpan_gc', unit, gc_time,
+      higher_is_better=False))
 
 
 class _OilpanGCTimesBase(page_test.PageTest):